diff --git a/app/controllers/api/v1/omniauth_callbacks_controller.rb b/app/controllers/api/v1/omniauth_callbacks_controller.rb
index 1618c47331..8f4d16aab1 100644
--- a/app/controllers/api/v1/omniauth_callbacks_controller.rb
+++ b/app/controllers/api/v1/omniauth_callbacks_controller.rb
@@ -1,7 +1,6 @@
 module Api
   module V1
     class OmniauthCallbacksController < Devise::OmniauthCallbacksController
-      include TwitterAuthentication
       include FacebookAuthentication
       include SlackAuthentication
       include GoogleAuthentication
@@ -21,7 +20,6 @@ def failure
       end
 
       def setup
-        setup_twitter if request.env['omniauth.strategy'].is_a?(OmniAuth::Strategies::Twitter)
         setup_facebook if request.env['omniauth.strategy'].is_a?(OmniAuth::Strategies::Facebook)
         render plain: 'Setup complete.', status: 404
       end
diff --git a/app/controllers/api/v1/registrations_controller.rb b/app/controllers/api/v1/registrations_controller.rb
deleted file mode 100644
index 4ceefa72a5..0000000000
--- a/app/controllers/api/v1/registrations_controller.rb
+++ /dev/null
@@ -1,80 +0,0 @@
-class Api::V1::RegistrationsController < Devise::RegistrationsController
-  before_action :configure_sign_up_params, only: [:create]
-  before_action :configure_account_update_params, only: [:update]
-
-  respond_to :json
-
-  include RegistrationsDoc
-
-  # POST /resource
-  def create
-    # super
-    build_resource(sign_up_params)
-
-    begin
-      duplicate_user = User.get_duplicate_user(resource.email, [])[:user]
-      user = resource
-      error = [
-        {
-          message: I18n.t(:email_exists)
-        }
-      ]
-      if !duplicate_user.nil? && duplicate_user.invited_to_sign_up?
-        duplicate_user.last_accepted_terms_at = Time.now
-        duplicate_user.save!
-      else
-        resource.last_accepted_terms_at = Time.now
-        resource.save!
-      end
-
-      render_success user, 'user', 401, error
-    rescue ActiveRecord::RecordInvalid => e
-      # Check if the error is specifically related to the email being taken
-      if resource.errors.details[:email].any? { |email_error| email_error[:error] == :taken } && resource.errors.details.except(:email).empty?
-        render_success nil, 'user', 401, error
-      else
-        # For other errors, show the error message in the form
-        clean_up_passwords resource
-        set_minimum_password_length
-        render_error e.message.gsub("Email #{I18n.t(:email_exists)}<br />", '').strip, 'INVALID_VALUE', 401
-      end
-    end
-  end
-
-  # PUT /resource
-  def update
-    # super
-    self.resource = resource_class.to_adapter.get!(send(:"current_#{resource_name}").to_key)
-
-    resource_updated = update_resource(resource, account_update_params)
-    User.current = resource
-
-    if resource_updated
-      sign_in resource, scope: resource_name, bypass_sign_in: true
-      render_success 'user', resource
-    else
-      clean_up_passwords resource
-      render_error 'Could not update user: ' + resource.errors.full_messages.join(', '), 'INVALID_VALUE'
-    end
-  end
-
-  # DELETE /resource
-  def destroy
-    # super
-    resource.destroy
-    Devise.sign_out_all_scopes ? sign_out : sign_out(resource_name)
-    render_success
-  end
-
-  protected
-
-  # If you have extra params to permit, append them to the sanitizer.
-  def configure_sign_up_params
-    devise_parameter_sanitizer.permit(:sign_up, keys: [:name, :login, :password, :password_confirmation, :image])
-  end
-
-  # If you have extra params to permit, append them to the sanitizer.
-  def configure_account_update_params
-    devise_parameter_sanitizer.permit(:account_update, keys: [:name, :password, :password_confirmation, :current_password])
-  end
-end
diff --git a/app/controllers/concerns/twitter_authentication.rb b/app/controllers/concerns/twitter_authentication.rb
deleted file mode 100644
index a8d1cd0af8..0000000000
--- a/app/controllers/concerns/twitter_authentication.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-module TwitterAuthentication
-  extend ActiveSupport::Concern
-
-  def setup_twitter
-    prefix = params[:context].to_s == 'smooch' ? 'smooch_' : ''
-    request.env['omniauth.strategy'].options[:consumer_key] = CheckConfig.get("#{prefix}twitter_consumer_key")
-    request.env['omniauth.strategy'].options[:consumer_secret] = CheckConfig.get("#{prefix}twitter_consumer_secret")
-  end
-
-  # OAuth callback
-  def twitter
-    request.env['omniauth.auth']['url'] = 'https://twitter.com/' + request.env['omniauth.auth'].info.nickname
-    start_session_and_redirect
-  end
-end
diff --git a/app/mailers/registration_mailer.rb b/app/mailers/registration_mailer.rb
deleted file mode 100644
index 7c03b947cf..0000000000
--- a/app/mailers/registration_mailer.rb
+++ /dev/null
@@ -1,19 +0,0 @@
-class RegistrationMailer < ApplicationMailer
-  layout nil
-
-  def welcome_email(user, password=nil)
-    @user = user
-    @user.password ||= password
-    @url = CheckConfig.get('checkdesk_client')
-    mail(to: @user.email, subject: I18n.t("mails_notifications.register.subject", app_name: CheckConfig.get('app_name'))) unless @user.email.blank?
-  end
-
-  def duplicate_email_detection(user, provider)
-    @user = user
-    @duplicate_provider =  provider.blank? ? I18n.t("mails_notifications.duplicated.email") : provider
-    @user_provider = user.encrypted_password? ? I18n.t("mails_notifications.duplicated.email") : user.get_user_provider(user.email)
-    @body_key = (provider.blank? && user.encrypted_password?) ? "both_emails" : "one_email"
-    mail(to: @user.email, subject: I18n.t("mails_notifications.duplicated.subject", app_name: CheckConfig.get('app_name'))) unless @user.email.blank?
-  end
-
-end
diff --git a/app/models/concerns/user_invitation.rb b/app/models/concerns/user_invitation.rb
index 55c7b152e8..3b9c755273 100644
--- a/app/models/concerns/user_invitation.rb
+++ b/app/models/concerns/user_invitation.rb
@@ -21,7 +21,7 @@ def self.send_user_invitation(members, text=nil)
               user = User.invite!({:email => email, :name => email.split("@").first, :invitation_role => role, :invitation_text => text}, User.current) do |iu|
                 iu.skip_invitation = true
               end
-              user.update_column(:raw_invitation_token, user.raw_invitation_token)
+              user.update_columns(raw_invitation_token: user.raw_invitation_token, encrypted_password: nil)
             else
               u.invitation_role = role
               u.invitation_text = text
@@ -110,17 +110,20 @@ def is_invited?(team = nil)
     private
 
     def create_team_user_invitation(options = {})
-      tu = TeamUser.new
-      tu.user_id = self.id
-      tu.team_id = Team.current.id
-      tu.role = self.invitation_role
-      tu.status = 'invited'
-      tu.invited_by_id = self.invited_by_id
-      tu.invited_by_id ||= User.current.id unless User.current.nil?
-      tu.invitation_token = self.invitation_token || options[:enc]
-      tu.raw_invitation_token = self.read_attribute(:raw_invitation_token) || self.raw_invitation_token || options[:raw]
-      tu.invitation_email = options[:email] || self.email
-      self.send_invitation_mail(tu) if tu.save!
+      team_id = Team.current&.id
+      unless team_id.nil?
+        tu = TeamUser.new
+        tu.user_id = self.id
+        tu.team_id = team_id
+        tu.role = self.invitation_role
+        tu.status = 'invited'
+        tu.invited_by_id = self.invited_by_id
+        tu.invited_by_id ||= User.current.id unless User.current.nil?
+        tu.invitation_token = self.invitation_token || options[:enc]
+        tu.raw_invitation_token = self.read_attribute(:raw_invitation_token) || self.raw_invitation_token || options[:raw]
+        tu.invitation_email = options[:email] || self.email
+        self.send_invitation_mail(tu) if tu.save!
+      end
     end
 
     def self.accept_team_user_invitation(tu, token, options)
diff --git a/app/models/concerns/user_multi_auth_login.rb b/app/models/concerns/user_multi_auth_login.rb
index 146d8283de..393e2c42eb 100644
--- a/app/models/concerns/user_multi_auth_login.rb
+++ b/app/models/concerns/user_multi_auth_login.rb
@@ -15,7 +15,8 @@ def self.from_omniauth(auth, current_user=nil)
       duplicate_user.accept_invitation_or_confirm unless duplicate_user.nil?
       u = self.check_merge_users(u, current_user, duplicate_user)
       u ||= current_user
-      user = self.create_omniauth_user(u, auth)
+      raise I18n.t('errors.messages.restrict_registration_to_invited_users_only') if u.nil?
+      user = self.update_omniauth_user(u, auth)
       User.create_omniauth_account(auth, user) unless auth.url.blank? || auth.provider.blank?
       user.reload
     end
@@ -39,11 +40,11 @@ def self.check_merge_users(u, current_user, duplicate_user)
       u
     end
 
-    def self.create_omniauth_user(u, auth)
-      user = u.nil? ? User.new : u
+    def self.update_omniauth_user(u, auth)
+      user = u
       user.email = user.email.presence || auth.info.email
       user.name = user.name.presence || auth.info.name
-      user.login = auth.info.nickname || auth.info.name.tr(' ', '-').downcase
+      user.login = auth.info.nickname.blank? ? auth.info.name.tr(' ', '-').downcase : auth.info.nickname
       user.from_omniauth_login = true
       user.skip_confirmation!
       user.last_accepted_terms_at = Time.now if user.last_accepted_terms_at.nil?
diff --git a/app/models/concerns/user_private.rb b/app/models/concerns/user_private.rb
index c48d1d8b99..f5962c0cfc 100644
--- a/app/models/concerns/user_private.rb
+++ b/app/models/concerns/user_private.rb
@@ -25,18 +25,7 @@ def set_token
   end
 
   def set_login
-    if self.login.blank?
-      if self.email.blank?
-        self.login = self.name.tr(' ', '-').downcase
-      else
-        self.login = self.email.split('@')[0]
-      end
-    end
-  end
-
-  def send_welcome_email
-    config_value = JSON.parse(CheckConfig.get('send_welcome_email_on_registration').to_s)
-    RegistrationMailer.delay.welcome_email(self) if self.encrypted_password? && config_value && !self.is_invited?
+    self.login = self.email.split('@')[0] if self.login.blank?
   end
 
   def user_is_member_in_current_team
@@ -53,7 +42,10 @@ def validate_duplicate_email
     duplicate = User.get_duplicate_user(self.email, self.id)
     unless duplicate[:user].nil?
       errors.add(:email, I18n.t(:email_exists)) if duplicate[:type] == 'Account'
-      handle_duplicate_email(duplicate[:user])
+      unless duplicate[:user].is_active?
+        self.errors.clear
+        errors.add(:base, I18n.t(:banned_user, app_name: CheckConfig.get('app_name'), support_email: CheckConfig.get('support_email')))
+      end
       return false
     end
   end
@@ -63,16 +55,6 @@ def password_complexity
     errors.add :password, I18n.t(:error_password_not_strong)
   end
 
-  def handle_duplicate_email(u)
-    if u.is_active?
-      provider = u.get_user_provider(self.email)
-      RegistrationMailer.delay.duplicate_email_detection(self, provider) if self.new_record?
-    else
-      self.errors.clear
-      errors.add(:base, I18n.t(:banned_user, app_name: CheckConfig.get('app_name'), support_email: CheckConfig.get('support_email')))
-    end
-  end
-
   def skip_confirmation_for_non_email_provider
     self.skip_confirmation! if self.from_omniauth_login && self.skip_confirmation_mail.nil?
   end
diff --git a/app/models/user.rb b/app/models/user.rb
index 26366dc48d..5a67fcb38c 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -30,12 +30,11 @@ class ToSOrPrivacyPolicyReadError < StandardError; end
   has_many :api_keys
   has_many :explainers
 
-  devise :registerable,
-         :recoverable, :rememberable, :trackable, :validatable, :confirmable,
+  devise :recoverable, :rememberable, :trackable, :validatable, :confirmable,
          :omniauthable, omniauth_providers: [:twitter, :facebook, :slack, :google_oauth2]
 
   before_create :skip_confirmation_for_non_email_provider, :set_last_received_terms_email_at
-  after_create :create_source_and_account, :set_source_image, :send_welcome_email
+  after_create :create_source_and_account, :set_source_image
   before_save :set_token, :set_login
   after_update :set_blank_email_for_unconfirmed_user
   before_destroy :freeze_account_ids_and_source_id
@@ -174,23 +173,9 @@ def is_member_of?(team)
   end
 
   def handle
-    self.email.blank? ? get_provider_from_user_account : self.email
-  end
-
-  def get_provider_from_user_account
-    account = self.get_social_accounts_for_login
-    account = account.first unless account.nil?
-    return nil if account.nil?
-    provider = account.provider.capitalize
-    if !account.omniauth_info.nil?
-      if account.provider == 'slack'
-        provider = account.omniauth_info.dig('extra', 'raw_info', 'url')
-      else
-        provider = account.omniauth_info.dig('url')
-        return provider if !provider.nil?
-      end
-    end
-    "#{self.login} at #{provider}"
+    # As we must invite users first then the email must exists
+    # which means the handle is email address
+    self.email
   end
 
   # Whether two users are members of any same team
diff --git a/app/views/registration_mailer/duplicate_email_detection.html.erb b/app/views/registration_mailer/duplicate_email_detection.html.erb
deleted file mode 100644
index 1c089ce856..0000000000
--- a/app/views/registration_mailer/duplicate_email_detection.html.erb
+++ /dev/null
@@ -1,93 +0,0 @@
-<%= render "shared/header" %>
-
-  <style>
-    @media only screen and (max-width: 481px) {
-      .notify-title a {
-        display: block !important;
-        width: auto !important;
-      }
-    }
-
-
-    @media only screen and (max-width: 601px) {
-      .notify-title__content {
-        padding: 0 30px;
-      }
-    }
-
-
-    @media only screen and (max-width: 481px) {
-      .notify-title__content {
-        padding: 0 !important;
-      }
-    }
-  </style>
-
-  <!--~~// Notify-title module start \\~~-->
-  <!--————————————————————————————-->
-  <div class="notify-title" style="text-align: left !important; direction: <%= @direction[:dir] %>">
-    <table cellpadding="0" cellspacing="0" border="0" width="100%" style="border-collapse: collapse; mso-table-lspace: 0pt; mso-table-rspace: 0pt;">
-      <tr>
-        <td style="border-collapse: collapse; font-size: 44px; line-height: 1; text-decoration: none !important;">&nbsp;</td>
-      </tr>
-    </table>
-    <div class="container " width="600" style="margin: 0 auto; text-align: <%= @direction[:align] %>; width: 600px;">
-      <table class="container__table" cellpadding="0" cellspacing="0" border="0" width="100%" style="border-collapse: collapse; margin: 0 auto; mso-table-lspace: 0pt; mso-table-rspace: 0pt; table-layout: fixed;">
-                <tr>
-                  <th class="col-1" style="font-weight: normal; mso-line-height-rule: exactly; padding: 0;" width="600px" valign="top" align="left">
-                    <div class="notify-title__content" style="text-align:<%= @direction[:align] %>;">
-                      <div class="h3 notify-title__proj" style="font-size: 21px; letter-spacing: -0.2px; line-height: 29px;">
-                        <%= I18n.t("mails_notifications.greeting_anonymous") %>
-                      </div>
-                      <table cellpadding="0" cellspacing="0" border="0" width="100%" style="border-collapse: collapse; mso-table-lspace: 0pt; mso-table-rspace: 0pt;">
-                        <tr>
-                          <td style="border-collapse: collapse; font-size: 13px; line-height: 1; text-decoration: none !important;">&nbsp;</td>
-                        </tr>
-                      </table>
-                      <div class="h1 notify-title__header" style="font-size: 40px; font-weight: bold; letter-spacing: -0.8px; line-height: 40px;">
-                        <%= I18n.t("mails_notifications.duplicated.header_title") %>
-                      </div>
-                      <table cellpadding="0" cellspacing="0" border="0" width="100%" style="border-collapse: collapse; mso-table-lspace: 0pt; mso-table-rspace: 0pt;">
-                        <tr>
-                          <td style="border-collapse: collapse; font-size: 12px; line-height: 1; text-decoration: none !important;">&nbsp;</td>
-                        </tr>
-                      </table>
-                      <div class="text-gray" style="color: #757575 !important;">
-                        <div class="h3" style="font-size: 21px; letter-spacing: -0.2px; line-height: 30px;">
-                          <%= 
-	                          I18n.t("mails_notifications.duplicated.#{@body_key}", user_email: @user.email, user_provider: @user_provider, duplicate_provider: @duplicate_provider, app_name: CheckConfig.get('app_name'), support_email: CheckConfig.get('support_email')).html_safe
-                          %>
-                        </div>
-                      </div>
-                    </div>
-                    
-                    <table cellpadding="0" cellspacing="0" border="0" width="100%" style="border-collapse: collapse; mso-table-lspace: 0pt; mso-table-rspace: 0pt;">
-                      <tr>
-                        <td style="border-collapse: collapse; font-size: 28px; line-height: 1; text-decoration: none !important;">&nbsp;</td>
-                      </tr>
-                    </table>
-
-                    <!--————————————————————————————-->
-                    <!--~~\\ Notify-title module end //~~-->
-
-                    <table cellpadding="0" cellspacing="0" border="0" width="100%" style="border-collapse: collapse; mso-table-lspace: 0pt; mso-table-rspace: 0pt;">
-                      <tr>
-                        <td style="border-collapse: collapse; font-size: 23px; line-height: 1; text-decoration: none !important;">&nbsp;</td>
-                      </tr>
-                    </table>
-                    <style>
-                      @media only screen and (max-width: 601px) {
-                        th.footer {
-                          padding: 0 30px !important;
-                        }
-                      }
-
-
-                      @media only screen and (max-width: 481px) {
-                        th.footer {
-                          padding: 0 !important;
-                        }
-                      }
-                    </style>
-
-<%= render "shared/footer" %>
diff --git a/app/views/registration_mailer/duplicate_email_detection.text.erb b/app/views/registration_mailer/duplicate_email_detection.text.erb
deleted file mode 100644
index ce4bdbe6ae..0000000000
--- a/app/views/registration_mailer/duplicate_email_detection.text.erb
+++ /dev/null
@@ -1,14 +0,0 @@
-<%= I18n.t("mails_notifications.greeting_anonymous") %>
-
-==========================================
-<%= I18n.t("mails_notifications.duplicated.header_title") %>
-==========================================
-
-<%= 
-  strip_tags I18n.t("mails_notifications.duplicated.#{@body_key}", user_email: @user.email, user_provider: @user_provider, duplicate_provider: @duplicate_provider, app_name: CheckConfig.get('app_name'), support_email: CheckConfig.get('support_email')).html_safe
-%>
-
-...
-
-<%= strip_tags I18n.t("mails_notifications.copyright_html", app_name: CheckConfig.get('app_name')) %>
-https://meedan.com
diff --git a/app/views/registration_mailer/welcome_email.html.erb b/app/views/registration_mailer/welcome_email.html.erb
deleted file mode 100644
index 4a49c640eb..0000000000
--- a/app/views/registration_mailer/welcome_email.html.erb
+++ /dev/null
@@ -1,133 +0,0 @@
-<%= render "shared/header" %>
-
-  <style>
-    @media only screen and (max-width: 481px) {
-      .notify-title a {
-        display: block !important;
-        width: auto !important;
-      }
-    }
-
-
-    @media only screen and (max-width: 601px) {
-      .notify-title__content {
-        padding: 0 30px;
-      }
-    }
-
-
-    @media only screen and (max-width: 481px) {
-      .notify-title__content {
-        padding: 0 !important;
-      }
-    }
-  </style>
-
-  <!--~~// Notify-title module start \\~~-->
-  <!--————————————————————————————-->
-  <div class="notify-title" style="text-align: <%= @direction[:align] %> !important; direction: <%= @direction[:dir] %>">
-            <table cellpadding="0" cellspacing="0" border="0" width="100%" style="border-collapse: collapse; mso-table-lspace: 0pt; mso-table-rspace: 0pt;">
-              <tr>
-                <td style="border-collapse: collapse; font-size: 44px; line-height: 1; text-decoration: none !important;">&nbsp;</td>
-              </tr>
-            </table>
-            <div class="container " width="600" style="margin: 0 auto; text-align: <%= @direction[:align] %>; width: 600px;">
-              <table class="container__table" cellpadding="0" cellspacing="0" border="0" width="100%" style="border-collapse: collapse; margin: 0 auto; mso-table-lspace: 0pt; mso-table-rspace: 0pt; table-layout: fixed;">
-                <tr>
-                  <th class="col-1" style="font-weight: normal; mso-line-height-rule: exactly; padding: 0;" width="600px" valign="top" align="<%= @direction[:align] %>">
-                    <div class="notify-title__content" style="text-align:<%= @direction[:align] %>;">
-                      <div class="h3 notify-title__proj" style="font-size: 21px; letter-spacing: -0.2px; line-height: 29px;">
-                      	<%= I18n.t("mails_notifications.greeting", username: @user.name) %>
-                      </div>
-                      <table cellpadding="0" cellspacing="0" border="0" width="100%" style="border-collapse: collapse; mso-table-lspace: 0pt; mso-table-rspace: 0pt;">
-                        <tr>
-                          <td style="border-collapse: collapse; font-size: 13px; line-height: 1; text-decoration: none !important;">&nbsp;</td>
-                        </tr>
-                      </table>
-                      <div class="h1 notify-title__header" style="font-size: 40px; font-weight: bold; letter-spacing: -0.8px; line-height: 40px;">
-                        <%= I18n.t(:mail_view_welcome, app_name: CheckConfig.get('app_name')) %>
-                      </div>
-                      <table cellpadding="0" cellspacing="0" border="0" width="100%" style="border-collapse: collapse; mso-table-lspace: 0pt; mso-table-rspace: 0pt;">
-                        <tr>
-                          <td style="border-collapse: collapse; font-size: 12px; line-height: 1; text-decoration: none !important;">&nbsp;</td>
-                        </tr>
-                      </table>
-                      <div class="text-gray" style="color: #757575 !important;">
-                        <div class="h3" style="font-size: 21px; letter-spacing: -0.2px; line-height: 30px;">
-                          <%= 
-                           I18n.t("mails_notifications.register.header_text", app_name: CheckConfig.get('app_name'), url: @url, password: @user.password).html_safe
-                          %>
-                        </div>
-                      </div>
-                    </div>
-                    
-                    <table cellpadding="0" cellspacing="0" border="0" width="100%" style="border-collapse: collapse; mso-table-lspace: 0pt; mso-table-rspace: 0pt;">
-                      <tr>
-                        <td style="border-collapse: collapse; font-size: 28px; line-height: 1; text-decoration: none !important;">&nbsp;</td>
-                      </tr>
-                    </table>
-
-                    <!--————————————————————————————-->
-                    <!--~~\\ Notify-title module end //~~-->
-
-                    <div class="container wide" width="600" style="margin: 0 auto; text-align: <%= @direction[:align] %>; width: 600px;">
-
-                      <table cellpadding="0" cellspacing="0" border="0" width="100%" style="border-collapse: collapse; mso-table-lspace: 0pt; mso-table-rspace: 0pt;">
-                        <tr>
-                          <td class="notify-title__button text-white" style="background: #2E77FC; border-collapse: collapse; border-radius: 4px; color: #f1f1f1 !important; display: inline-block; padding-bottom: 15px; padding-left: 25px; padding-right: 23px; padding-top: 15px;"
-                            width="auto">
-                            <table cellpadding="0" cellspacing="0" border="0" width="100%" style="border-collapse: collapse; mso-table-lspace: 0pt; mso-table-rspace: 0pt;">
-                              <tr>
-                                <td style="border-collapse: collapse; padding-right: 14px;">
-                                  <span class="span" style="font-size: 17px; font-weight: bold; line-height: 20px;">
-                                    <%=
-                                      link_to(I18n.t("mails_notifications.register.login_button", app_name: CheckConfig.get('app_name')), @url,
-                                          :style => "text-decoration: none !important;color: #fff !important;"
-                                        )
-                                    %>
-                                  </span>
-                                </td>
-                                <td style="border-collapse: collapse;" align="right">
-                                  <%= image_tag("https://images.ctfassets.net/g118h5yoccvd/#{@direction[:arrow]}", width: "7", alt: "arrow-icon",  style: "-ms-interpolation-mode: bicubic; border: 0 none; height: auto; line-height: 100%; outline: none; text-decoration: none;") %>
-                                </td>
-                              </tr>
-                            </table>
-                          </td>
-                        </tr>
-                      </table>
-
-                      <table cellpadding="0" cellspacing="0" border="0" width="100%" style="border-collapse: collapse; mso-table-lspace: 0pt; mso-table-rspace: 0pt;">
-                        <tr>
-                          <td style="border-collapse: collapse; font-size: 23px; line-height: 1; text-decoration: none !important;">&nbsp;</td>
-                        </tr>
-                      </table>
-
-                      <div class="text-gray" style="color: #757575 !important;">
-                        <div class="h3" style="font-size: 21px; letter-spacing: -0.2px; line-height: 30px;">
-													<%= t("mails_notifications.register.footer_text") %>
-                        </div>
-                      </div>
-
-                    </div>
-
-                    <table cellpadding="0" cellspacing="0" border="0" width="100%" style="border-collapse: collapse; mso-table-lspace: 0pt; mso-table-rspace: 0pt;">
-                      <tr>
-                        <td style="border-collapse: collapse; font-size: 23px; line-height: 1; text-decoration: none !important;">&nbsp;</td>
-                      </tr>
-                    </table>
-                    <style>
-                      @media only screen and (max-width: 601px) {
-                        th.footer {
-                          padding: 0 30px !important;
-                        }
-                      }
-
-
-                      @media only screen and (max-width: 481px) {
-                        th.footer {
-                          padding: 0 !important;
-                        }
-                      }
-                    </style>
-
-<%= render "shared/footer" %>
diff --git a/app/views/registration_mailer/welcome_email.text.erb b/app/views/registration_mailer/welcome_email.text.erb
deleted file mode 100644
index 2f0ba25b24..0000000000
--- a/app/views/registration_mailer/welcome_email.text.erb
+++ /dev/null
@@ -1,19 +0,0 @@
-<%= I18n.t("mails_notifications.greeting", username: @user.name) %>
-
-==========================================
-<%= I18n.t(:mail_view_welcome, app_name: CheckConfig.get('app_name')) %>
-==========================================
-
-<%= 
-	strip_tags I18n.t("mails_notifications.register.header_text", app_name: CheckConfig.get('app_name'), url: @url, password: @user.password)
-%>
-
-<%= I18n.t("mails_notifications.register.login_button", app_name: CheckConfig.get('app_name')) %>
-<%= @url %>
-
-<%= t("mails_notifications.register.footer_text") %>
-
-...
-
-<%= strip_tags I18n.t("mails_notifications.copyright_html", app_name: CheckConfig.get('app_name')) %>
-https://meedan.com
diff --git a/config/locales/en.yml b/config/locales/en.yml
index 0cca7eb910..34d967b424 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -113,6 +113,7 @@ en:
       invalid_feed_saved_search_value: Should belong to a workspace that is part of this feed.
       invalid_feed_saved_search_list_type: The saved search list type is invalid.
       platform_allowed_values_error: 'cannot be of type %{type}, allowed types: %{allowed_types}'
+      restrict_registration_to_invited_users_only: 'Looks like you don’t have an invitation yet. Please request one from your workspace.'
   activerecord:
     models:
       link: Link
diff --git a/config/routes.rb b/config/routes.rb
index a790b10c50..682ae2d413 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -34,7 +34,7 @@
       match '/admin/smooch_bot/:id/authorize/instagram' => 'admin#save_instagram_credentials_for_smooch_bot', via: [:get]
       match '/project_medias/:id/oembed' => 'project_medias#oembed', via: [:get], defaults: { format: :json }
       match '/webhooks/:name' => 'webhooks#index', via: [:post, :get], defaults: { format: :json }
-      devise_for :users, controllers: { invitations: 'api/v1/invitations', sessions: 'api/v1/sessions', registrations: 'api/v1/registrations', omniauth_callbacks: 'api/v1/omniauth_callbacks', confirmations: 'api/v1/confirmations' }
+      devise_for :users, controllers: { invitations: 'api/v1/invitations', sessions: 'api/v1/sessions', omniauth_callbacks: 'api/v1/omniauth_callbacks', confirmations: 'api/v1/confirmations' }
       devise_scope :api_user do
         get '/users/logout', to: 'omniauth_callbacks#logout'
         get '/users/auth/twitter/setup' => 'omniauth_callbacks#setup'
diff --git a/lib/sample_data.rb b/lib/sample_data.rb
index 6f5a9ad1d7..5e8ec926bd 100644
--- a/lib/sample_data.rb
+++ b/lib/sample_data.rb
@@ -139,7 +139,20 @@ def create_user(options = {})
     u.reload
   end
 
+  def invite_new_user(options = {})
+    email = options.has_key?(:email) ? options[:email] : "#{random_string}@#{random_string}.com"
+    name = options.has_key?(:name) ? options[:name] : random_string
+    user = User.invite!(email: email, name: name) do |u|
+      u.skip_invitation = true
+    end
+    user.update_column(:encrypted_password, nil)
+    user
+  end
+
   def create_omniauth_user(options = {})
+    # Invite user first
+    options[:email] ||= "#{random_string}@#{random_string}.com"
+    invite_new_user(options)
     u_current = User.current
     url = if options.has_key?(:url)
             options[:url]
@@ -154,11 +167,11 @@ def create_omniauth_user(options = {})
     end
     options[:uid] = options[:uuid] if options.has_key?(:uuid)
     auth = {}
-    provider = options.has_key?(:provider) ? options[:provider] : %w(twitter facebook).sample
-    email = options.has_key?(:email) ? options[:email] : "#{random_string}@#{random_string}.com"
+    provider = options.has_key?(:provider) ? options[:provider] : %w(google slack).sample
     auth[:uid] = options.has_key?(:uid) ? options[:uid] : random_string
     auth[:url] = url
-    auth[:info] = options.has_key?(:info) ? options[:info] : {name: random_string, email: email}
+    options[:info][:email] = options[:email] if options.has_key?(:info) && options[:info][:email].nil?
+    auth[:info] = options.has_key?(:info) ? options[:info] : {name: random_string, email: options[:email]}
     auth[:credentials] = options.has_key?(:credentials) ? options[:credentials] : {token: random_string, secret: random_string}
     auth[:extra] = options.has_key?(:extra) ? options[:extra] : {}
     current_user = options.has_key?(:current_user) ? options[:current_user] : nil
diff --git a/test/controllers/base_api_controller_test.rb b/test/controllers/base_api_controller_test.rb
index 3991da0b19..10b9989765 100644
--- a/test/controllers/base_api_controller_test.rb
+++ b/test/controllers/base_api_controller_test.rb
@@ -41,23 +41,23 @@ def setup
   end
 
   test "should get current user from session" do
-    u = create_omniauth_user info: {name: 'Test User'}
+    u = create_omniauth_user email: 'test@local.com', info: {name: 'Test User'}
     authenticate_with_user(u)
     get :me, params: {}
     assert_response :success
     response = JSON.parse(@response.body)
-    assert_equal 'Test User', response['data']['name']
+    assert_equal 'test@local.com', response['data']['email']
     assert_equal 'session', response['data']['source']
   end
 
   test "should get current user from token" do
-    u = create_omniauth_user info: {name: 'Test User'}
+    u = create_omniauth_user email: 'test@local.com', info: { name: 'Test User', email: 'test@local.com' }
     header = CheckConfig.get('authorization_header') || 'X-Token'
     @request.headers.merge!({ header => u.token })
     get :me, params: {}
     assert_response :success
     response = JSON.parse(@response.body)
-    assert_equal 'Test User', response['data']['name']
+    assert_equal 'test@local.com', response['data']['email']
     assert_equal 'token', response['data']['source']
   end
 
diff --git a/test/controllers/omniauth_callbacks_controller_test.rb b/test/controllers/omniauth_callbacks_controller_test.rb
index 56165f4b89..fb7e6365d1 100644
--- a/test/controllers/omniauth_callbacks_controller_test.rb
+++ b/test/controllers/omniauth_callbacks_controller_test.rb
@@ -5,19 +5,6 @@ def setup
     super
     @controller = Api::V1::OmniauthCallbacksController.new
     OmniAuth.config.test_mode = true
-    OmniAuth.config.mock_auth[:twitter] = OmniAuth::AuthHash.new({
-      provider: 'twitter',
-      uid: '654321',
-      info: {
-        name: 'Test',
-        image: 'http://twitter.com/test/image.png',
-        nickname: 'test'
-      },
-      credentials: {
-        token: '123456',
-        secret: 'top_secret'
-      }
-    })
     OmniAuth.config.mock_auth[:facebook] = OmniAuth::AuthHash.new({
       provider: 'facebook',
       uid: '654321',
@@ -77,8 +64,11 @@ def setup
         secret: 'top_secret'
       }
     })
+    [{email: 'test@test.com', name: 'Test'}, {email: 'sawy@meedan.com', name: 'Mohamed El-Sawy'}].each do |info|
+      invite_new_user info
+    end
     request.env['devise.mapping'] = Devise.mappings[:api_user]
-    ['https://twitter.com/test', 'https://facebook.com/654321', 'https://www.googleapis.com/plus/v1/people/654321'].each do |url|
+    ['https://facebook.com/654321', 'https://www.googleapis.com/plus/v1/people/654321'].each do |url|
       WebMock.stub_request(:get, CheckConfig.get('pender_url_private') + '/api/medias').with({ query: { url: url } }).to_return(body: '{"type":"media","data":{"type":"profile"}}')
     end
     User.current = nil
@@ -89,25 +79,6 @@ def teardown
     User.current = nil
   end
 
-  test "should redirect to root after Twitter authentication" do
-    request.env['omniauth.auth'] = OmniAuth.config.mock_auth[:twitter]
-    get :twitter, params: {}
-    assert_redirected_to '/close.html'
-  end
-
-  test "should set information in session after Twitter authentication" do
-    request.env['omniauth.auth'] = OmniAuth.config.mock_auth[:twitter]
-    assert_nil session['checkdesk.user']
-    get :twitter, params: {}
-    assert_not_nil session['checkdesk.current_user_id']
-  end
-
-  test "should redirect to destination after Twitter authentication" do
-    request.env['omniauth.auth'] = OmniAuth.config.mock_auth[:twitter]
-    get :twitter, params: { destination: '/close.html' }
-    assert_redirected_to '/close.html'
-  end
-
   test "should set information in session after Facebook authentication" do
     request.env['omniauth.auth'] = OmniAuth.config.mock_auth[:facebook]
     assert_nil session['checkdesk.user']
@@ -190,12 +161,11 @@ def teardown
   end
 
   test "should connect when current user set" do
-    p1 = random_complex_password
-    u = create_user login: 'test', password: p1, password_confirmation: p1, email: 'test@test.com'
+    u = User.where(email: 'test@test.com').first
     u.confirm
     authenticate_with_user(u)
-    request.env['omniauth.auth'] = OmniAuth.config.mock_auth[:twitter]
-    get :twitter, params: {}
+    request.env['omniauth.auth'] = OmniAuth.config.mock_auth[:facebook]
+    get :facebook, params: {}
     u = User.find(u.id)
     assert_equal 1, u.source.accounts.count
   end
@@ -219,12 +189,6 @@ def teardown
     assert_redirected_to '/close.html'
   end
 
-  test "should setup Twitter authentication" do
-    request.env['omniauth.strategy'] = OmniAuth::Strategies::Twitter.new({})
-    get :setup, params: {}
-    assert_response 404
-  end
-
   test "should setup Facebook authentication" do
     request.env['omniauth.strategy'] = OmniAuth::Strategies::Facebook.new({})
     get :setup, params: {}
diff --git a/test/controllers/registrations_controller_test.rb b/test/controllers/registrations_controller_test.rb
deleted file mode 100644
index 46ca89c0bf..0000000000
--- a/test/controllers/registrations_controller_test.rb
+++ /dev/null
@@ -1,167 +0,0 @@
-require_relative '../test_helper'
-
-class RegistrationsControllerTest < ActionController::TestCase
-  def setup
-    super
-    @controller = Api::V1::RegistrationsController.new
-    @request.env["devise.mapping"] = Devise.mappings[:api_user]
-    User.current = nil
-    Team.current = nil
-  end
-
-  def teardown
-    super
-    User.current = nil
-    Team.current = nil
-  end
-
-  test "should create user" do
-    p1 = random_complex_password
-    assert_difference 'User.count' do
-      post :create, params: { api_user: { password: p1, password_confirmation: p1, email: 't@test.com', login: 'test', name: 'Test' } }
-      assert_response 401 # needs to confirm before login
-    end
-  end
-
-  test "should create user if invited" do
-    t = create_team
-    u = create_user
-    email = 'test@local.com'
-    create_team_user team: t, user: u, role: 'admin'
-    with_current_user_and_team(u, t) do
-      members = [{role: 'collaborator', email: email}]
-      User.send_user_invitation(members)
-    end
-    User.current = Team.current = nil
-    p1 = random_complex_password
-    assert_no_difference 'User.count' do
-      post :create, params: { api_user: { password: p1, password_confirmation: p1, email: email, login: 'test', name: 'Test' } }
-      assert_response 401
-    end
-  end
-
-  test "should create user if confirmed" do
-    p1 = random_complex_password
-    User.any_instance.stubs(:confirmation_required?).returns(false)
-    assert_difference 'User.count' do
-      post :create, params: { api_user: { password: p1, password_confirmation: p1, email: 't@test.com', login: 'test', name: 'Test' } }
-      assert_response 401
-    end
-    User.any_instance.unstub(:confirmation_required?)
-  end
-
-  test "should not create user if password is missing" do
-    p1 = random_complex_password
-    assert_no_difference 'User.count' do
-      post :create, params: { api_user: { password_confirmation: p1, email: 't@test.com', login: 'test', name: 'Test' } }
-      assert_response 401
-    end
-  end
-
-  test "should not create user if password is too short" do
-    p1 = '1234'
-    assert_no_difference 'User.count' do
-      post :create, params: { api_user: { password: p1, password_confirmation: p1, email: 't@test.com', login: 'test', name: 'Test' } }
-      assert_response 401
-    end
-  end
-
-  test "should not create user if password don't match" do
-    p1 = random_complex_password
-    assert_no_difference 'User.count' do
-      post :create, params: { api_user: { password: random_complex_password, password_confirmation: random_complex_password, email: 't@test.com', login: 'test', name: 'Test' } }
-      assert_response 401
-    end
-  end
-
-  test "should not create user if email is not present" do
-    p1 = random_complex_password
-    assert_no_difference 'User.count' do
-      post :create, params: { api_user: { password: p1, password_confirmation: p1, email: '', login: 'test', name: 'Test' } }
-      assert_response 401
-    end
-  end
-
-  test "should create user if login is not present" do
-    p1 = random_complex_password
-    assert_difference 'User.count' do
-      post :create, params: { api_user: { password: p1, password_confirmation: p1, email: 't@test.com', login: '', name: 'Test' } }
-      assert_response 401 # needs to confirm before login
-    end
-  end
-
-  test "should not create user if name is not present" do
-    p1 = random_complex_password
-    assert_no_difference 'User.count' do
-      post :create, params: { api_user: { password: p1, password_confirmation: p1, email: 't@test.com', login: 'test', name: '' } }
-      assert_response 401
-    end
-  end
-
-  test "should update only a few attributes" do
-    p1 = random_complex_password
-    u = create_user name: 'Foo', login: 'test', token: 'test', email: 'foo@test.com', password: p1
-    authenticate_with_user(u)
-    post :update, params: { api_user: { name: 'Bar', login: 'bar', token: 'bar', email: 'bar@test.com', current_password: p1 } }
-    assert_response :success
-    u = u.reload
-    assert_equal 'Bar', u.name
-    assert_equal 'test', u.login
-    assert_equal 'test', u.token
-    assert_empty u.email
-    assert_equal 'bar@test.com', u.unconfirmed_email
-  end
-
-  test "should not update account if not logged in" do
-    p1 = random_complex_password
-    post :update, params: { api_user: { name: 'Bar', login: 'bar', token: 'bar', email: 'bar@test.com', current_password: p1 } }
-    assert_response 401
-  end
-
-  test "should not update account" do
-    p1 = random_complex_password
-    u = create_user name: 'Foo', login: 'test', token: 'test', email: 'foo@test.com', password: p1
-    authenticate_with_user(u)
-    post :update, params: { api_user: { name: 'Bar', login: 'bar', token: 'bar', email: 'bar@test.com', current_password: p1, password: '123', password_confirmation: '123' } }
-    assert_response 400
-    u = u.reload
-  end
-
-  test "should destroy account" do
-    p1 = random_complex_password
-    u = create_user name: 'Foo', login: 'test', token: 'test', email: 'foo@test.com', password: p1
-    authenticate_with_user(u)
-    assert_difference 'User.count', -1 do
-      delete :destroy, params: {}
-    end
-    assert_response :success
-  end
-
-  test "should not destroy account if not logged in" do
-    assert_no_difference 'User.count' do
-      delete :destroy, params: {}
-    end
-    assert_response 401
-  end
-
-  test "should return generic response in case of error when registering using an existing email" do
-    existing_user = create_user(email: 'existing@test.com')
-    p1 = random_complex_password
-
-    assert_no_difference 'User.count' do
-      post :create, params: { api_user: { password: p1, password_confirmation: p1, email: existing_user.email, login: 'test', name: 'Test' } }
-      assert_response 401
-      assert_equal 'Please check your email. If an account with that email doesn’t exist, you should have received a confirmation email. If you don’t receive a confirmation e-mail, try to reset your password or get in touch with our support.', response.parsed_body.dig("errors", 0, "message")
-    end
-  end
-
-  test "should return generic response when registering with non-existing email" do
-    p1 = random_complex_password
-
-    assert_difference 'User.count', 1 do
-      post :create, params: { api_user: { password: p1, password_confirmation: p1, email: 'non_existing@test.com', login: 'test', name: 'Test' } }
-      assert_response 401
-      assert_equal 'Please check your email. If an account with that email doesn’t exist, you should have received a confirmation email. If you don’t receive a confirmation e-mail, try to reset your password or get in touch with our support.', response.parsed_body.dig("errors", 0, "message")
-    end
-  end
-end
diff --git a/test/mailers/registration_mailer_test.rb b/test/mailers/registration_mailer_test.rb
deleted file mode 100644
index 0e7a2bb7df..0000000000
--- a/test/mailers/registration_mailer_test.rb
+++ /dev/null
@@ -1,28 +0,0 @@
-require_relative '../test_helper'
-
-class RegistrationMailerTest < ActionMailer::TestCase
-
-  test "should send welcome email" do
-    u = create_user email: 'test@localhost', password: 'testA@12'
-    email = RegistrationMailer.welcome_email(u)
-
-    assert_emails 1 do
-      email.deliver_now
-    end
-
-    assert_match email.from.first, CheckConfig.get('default_mail')
-    assert_equal ['test@localhost'], email.to
-    assert_match /testA@12/, email.body.parts.first.to_s
-  end
-
-  test "should send email for mail duplicate" do
-    u = create_user email: 'test@localhost'
-    email = RegistrationMailer.duplicate_email_detection(u, u)
-    assert_emails 1 do
-      email.deliver_now
-    end
-    assert_match email.from.first, CheckConfig.get('default_mail')
-    assert_equal ['test@localhost'], email.to
-  end
-
-end
diff --git a/test/models/user_test.rb b/test/models/user_test.rb
index cb8233a8ce..0c3a8eeb11 100644
--- a/test/models/user_test.rb
+++ b/test/models/user_test.rb
@@ -72,21 +72,13 @@ def setup
 
   test "should not require password if there is a provider" do
     assert_nothing_raised do
-      create_omniauth_user password: '', provider: 'twitter'
+      create_omniauth_user password: '', provider: 'slack'
     end
     assert_raises ActiveRecord::RecordInvalid do
       create_user password: ''
     end
   end
 
-  test "should not require email for omniauth user" do
-    u = nil
-    assert_nothing_raised do
-      u = create_omniauth_user email: ''
-    end
-    assert_equal '', u.reload.email
-  end
-
   test "should output json" do
     u = create_user
     assert_nothing_raised do
@@ -157,8 +149,8 @@ def setup
   end
 
   test "should set login from name" do
-    info = {login: '', nickname: '', name: 'Foo Bar'}
-    u = create_omniauth_user provider: 'facebook', info: info, email: ''
+    info = {login: '', nickname: '', name: 'Foo Bar', email: 'test@local.com'}
+    u = create_omniauth_user provider: 'facebook', info: info, email: 'test@local.com'
     assert_equal 'foo-bar', u.reload.login
   end
 
@@ -167,35 +159,6 @@ def setup
     assert_equal 'foobar', u.reload.login
   end
 
-  test "should send welcome email when user is created" do
-    stub_configs({ 'send_welcome_email_on_registration' => true }) do
-      assert_difference 'ActionMailer::Base.deliveries.size', 1 do
-        create_user skip_confirmation: true
-      end
-      assert_no_difference 'ActionMailer::Base.deliveries.size' do
-        create_omniauth_user provider: 'twitter', password: nil
-        create_omniauth_user provider: 'facebook', password: nil
-      end
-    end
-
-    stub_configs({ 'send_welcome_email_on_registration' => false }) do
-      assert_no_difference 'ActionMailer::Base.deliveries.size' do
-        create_user skip_confirmation: true
-        create_omniauth_user provider: 'twitter'
-        create_omniauth_user provider: 'facebook'
-      end
-    end
-  end
-
-  test "should send email when user email is duplicate" do
-    u = create_omniauth_user provider: 'facebook'
-    assert_difference 'ActionMailer::Base.deliveries.size', 1 do
-      assert_raises ActiveRecord::RecordInvalid do
-        create_user email: u.email
-      end
-    end
-  end
-
   test "should not add duplicate mail" do
     u = create_user
     create_account user: u, source: u.source, provider: 'slack', email: 'test@local.com'
@@ -381,7 +344,7 @@ def setup
   test "should not crash when creating user account" do
     Account.any_instance.stubs(:save).raises(Errno::ECONNREFUSED)
     assert_nothing_raised do
-      create_omniauth_user url: 'http://twitter.com/meedan', provider: 'twitter'
+      create_omniauth_user url: 'http://slack.com/meedan', provider: 'slack'
     end
     Account.any_instance.unstub(:save)
   end
@@ -461,13 +424,10 @@ def setup
   test "should get handle" do
     u = create_user email: 'user@email.com'
     assert_equal 'user@email.com', u.handle
-    u = create_omniauth_user provider: 'facebook', email: '', url: 'https://facebook.com/10157109339765023'
-    assert_equal 'https://facebook.com/10157109339765023', u.handle
-  end
-
-  test "should get handle for Slack" do
-    u = create_omniauth_user provider: 'slack', email: '', info: { name: 'caiosba' }, extra: { 'raw_info' => { 'url' => 'https://meedan.slack.com' } }
-    assert_equal 'caiosba at https://meedan.slack.com', u.handle
+    u = create_omniauth_user provider: 'facebook', email: 'test@local.com', url: 'https://facebook.com/10157109339765023'
+    assert_equal 'test@local.com', u.handle
+    u = create_omniauth_user provider: 'slack', email: 'test2@local.com', info: { name: 'caiosba' }, extra: { 'raw_info' => { 'url' => 'https://meedan.slack.com' } }
+    assert_equal 'test2@local.com', u.handle
   end
 
   test "should return whether two users are colleagues in a team" do
@@ -487,14 +447,14 @@ def setup
   end
 
   test "should require confirmation for e-mail accounts only" do
-    u = create_omniauth_user provider: 'twitter'
+    u = create_omniauth_user provider: 'slack'
     assert !u.send(:confirmation_required?)
     u = create_user confirm: false
     assert u.send(:confirmation_required?)
   end
 
   test "should require confirmation after update email" do
-    u = create_omniauth_user provider: 'twitter'
+    u = create_omniauth_user provider: 'slack'
     assert u.is_confirmed?
     u = create_user email: 'foo@bar.com', confirm: false
     assert_not u.is_confirmed?
@@ -574,18 +534,6 @@ def setup
     assert_equal '654321', a.reload.uid
   end
 
-  test "should not update Facebook id if email not set" do
-    u1 = create_omniauth_user provider: 'facebook', uid: '123456', email: ''
-    u2 = create_omniauth_user provider: 'facebook', uid: '456789', email: ''
-    a1 = u1.get_social_accounts_for_login({provider: 'facebook', uid: '123456'}).first
-    a2 = u2.get_social_accounts_for_login({provider: 'facebook', uid: '456789'}).first
-    assert_equal '123456', a1.uid
-    assert_equal '456789', a2.uid
-    User.update_facebook_uuid(OpenStruct.new({ provider: 'facebook',url: a1.url, uid: '456789', info: OpenStruct.new({ email: '' })}))
-    assert_equal '123456', a1.reload.uid
-    assert_equal '456789', a2.reload.uid
-  end
-
   test "should save valid languages" do
     u = create_user
     value = ["en"]
@@ -658,6 +606,7 @@ def setup
     auth = OpenStruct.new({ url: url, provider: 'facebook', uid: '1062518227129764', credentials: credentials, info: info})
     Account.any_instance.stubs(:save).returns(false)
     assert_difference 'User.count' do
+      invite_new_user email: 'user@fb.com', name: 'John'
       User.from_omniauth(auth)
     end
     u = User.find_by_email 'user@fb.com'
@@ -720,11 +669,11 @@ def setup
   end
 
   test "should set source image when call user from omniauth" do
-    u = create_omniauth_user provider: 'twitter', uid: '12345'
+    u = create_omniauth_user provider: 'slack', uid: '12345'
     assert_match /images\/user.png/, u.source.avatar
     credentials = OpenStruct.new({ token: '1234', secret: 'secret'})
     info = OpenStruct.new({ email: 'user@fb.com', name: 'John', image: 'picture.png' })
-    auth = OpenStruct.new({ provider: 'twitter', uid: '12345', credentials: credentials, info: info, url: random_url})
+    auth = OpenStruct.new({ provider: 'slack', uid: '12345', credentials: credentials, info: info, url: random_url})
     omniauth_info = {"info"=> { "image"=>"https://avatars.slack-edge.com/2016-08-30/74454572532_7b40a563ce751e1c1d50_192.jpg"} }
     Account.any_instance.stubs(:omniauth_info).returns(omniauth_info)
     User.from_omniauth(auth)
@@ -1025,20 +974,6 @@ def setup
     assert_not_empty result.errors
   end
 
-  test "should not send welcome email for invited user" do
-    t = create_team
-    u = create_user
-    create_team_user team: t, user: u, role: 'admin'
-    stub_configs({ 'send_welcome_email_on_registration' => true }) do
-      with_current_user_and_team(u, t) do
-        assert_difference 'ActionMailer::Base.deliveries.size', 1 do
-          members = [{role: 'collaborator', email: 'test1@local.com'}]
-          User.send_user_invitation(members)
-        end
-      end
-    end
-  end
-
   test "should send invitation using invitation email not primary email" do
     t = create_team
     u = create_user email: 'primary@local.com'
@@ -1089,14 +1024,14 @@ def setup
     u = create_user
     assert_no_difference 'User.count' do
       assert_difference 'Account.count', 1 do
-        create_omniauth_user provider: 'twitter', uid: '123456', current_user: u
+        create_omniauth_user provider: 'slack', uid: '123456', current_user: u
       end
     end
   end
 
   test "should get user through omniauth info" do
-    u = create_omniauth_user uid: '123456', provider: 'twitter'
-    assert_equal u, User.find_with_omniauth('123456', 'twitter')
+    u = create_omniauth_user uid: '123456', provider: 'slack'
+    assert_equal u, User.find_with_omniauth('123456', 'slack')
   end
 
   test "should get user through token" do
@@ -1105,7 +1040,7 @@ def setup
   end
 
   test "should get social accounts for login" do
-    u = create_omniauth_user provider: 'twitter'
+    u = create_omniauth_user provider: 'slack'
     a = create_account source: u.source, user: u, provider: 'facebook'
     a2 = create_account source: u.source, user: u, uid: ''
     assert_equal 2, u.get_social_accounts_for_login.count
@@ -1115,14 +1050,13 @@ def setup
   end
 
   test "should get user accounts and providers" do
-    u = create_omniauth_user provider: 'twitter'
+    u = create_omniauth_user provider: 'facebook'
     s = u.source
     omniauth_info = {"info"=> { "name" => "test" } }
     create_account source: s, user: u, provider: 'slack', uid: '123456', omniauth_info: omniauth_info
     create_account source: s, user: u, provider: 'slack', uid: '987654', omniauth_info: omniauth_info
     assert_equal 3, u.get_social_accounts_for_login.count
-    assert_equal 0, u.get_social_accounts_for_login({provider: 'facebook'}).count
-    assert_equal 1, u.get_social_accounts_for_login({provider: 'twitter'}).count
+    assert_equal 1, u.get_social_accounts_for_login({provider: 'facebook'}).count
     assert_equal 2, u.get_social_accounts_for_login({provider: 'slack'}).count
     assert_equal 1, u.get_social_accounts_for_login({provider: 'slack', uid: '123456'}).count
     providers = u.providers
@@ -1137,8 +1071,8 @@ def setup
   end
 
   test "should disconnect social account" do
-    u = create_omniauth_user provider: 'twitter', uid: '123456'
-    u.disconnect_login_account('twitter', '123456')
+    u = create_omniauth_user provider: 'slack', uid: '123456'
+    u.disconnect_login_account('slack', '123456')
     assert_equal 0, u.get_social_accounts_for_login.count
     u2 = create_omniauth_user provider: 'slack', uid: '456789'
     a = u2.get_social_accounts_for_login({provider: 'slack', uid: '456789'}).first
@@ -1163,30 +1097,17 @@ def setup
         create_omniauth_user email: u.email
       end
     end
-    u = create_omniauth_user provider: 'twitter', email: '', uid: '123456'
-    u2 = create_omniauth_user provider: 'facebook', email: 'test@local.com'
-    tu = create_team_user user: u2
-    pm = create_project_media user: u2
-    s2_id = u2.source.id
-    u2_id = u2.id
-    u3 = create_omniauth_user provider: 'twitter', uid: '123456', email: 'test@local.com'
-    assert_equal u.id, u3.id
+    u = create_omniauth_user provider: 'google', email: 'test@local.com', uid: '123456'
+    u2 = create_omniauth_user provider: 'slack', email: 'test@local.com', uid: '456789'
+    assert_equal u.id, u2.id
     accounts = u.source.accounts
     assert_equal 2, accounts.count
-    assert_equal ['facebook', 'twitter'].sort, accounts.map(&:provider).sort
-    assert_equal u.id, pm.reload.user_id
-    assert_equal u.id, tu.reload.user_id
-    assert_raises ActiveRecord::RecordNotFound do
-      User.find(u2_id)
-    end
-    assert_raises ActiveRecord::RecordNotFound do
-      Source.find(s2_id)
-    end
+    assert_equal ['google', 'slack'].sort, accounts.map(&:provider).sort
   end
 
   test "should keep higher role when merge accounts in same team" do
     t = create_team
-    u = create_omniauth_user provider: 'twitter', email: 'test@local.com'
+    u = create_omniauth_user provider: 'slack', email: 'test@local.com'
     u2 = create_omniauth_user provider: 'facebook', email: 'test2@local.com'
     create_team_user team: t, user: u, role: 'collaborator'
     create_team_user team: t, user: u2, role: 'editor'
@@ -1197,18 +1118,18 @@ def setup
   end
 
   test "should merge two existing accounts" do
-    u = create_omniauth_user provider: 'twitter', email: '', uid: '123456'
-    u2 = create_omniauth_user provider: 'twitter', email: '', uid: '345678'
+    u = create_omniauth_user provider: 'facebook', email: 'test@local.com', uid: '123456'
+    u2 = create_omniauth_user provider: 'facebook', email: 'test2@local.com', uid: '345678'
     assert_no_difference 'User.count' do
-      create_omniauth_user provider: 'twitter', email: 'test_a@local.com', uid: '123456'
+      create_omniauth_user provider: 'facebook', email: 'test_a@local.com', uid: '123456'
     end
-    create_omniauth_user provider: 'twitter', email: 'test_b@local.com', uid: '345678', current_user: u
+    create_omniauth_user provider: 'facebook', email: 'test_b@local.com', uid: '345678', current_user: u
     assert_equal 2, u.source.accounts.count
     assert_raises ActiveRecord::RecordNotFound do
       User.find(u2.id)
     end
     # test connect with same provider
-    create_omniauth_user provider: 'twitter', email: 'test_a@local.com', uid: '123456', current_user: u
+    create_omniauth_user provider: 'facebook', email: 'test_a@local.com', uid: '123456', current_user: u
   end
 
   test "should merge two users with same source" do