Merge pull request #5703 from wso2/fixing-product-is-issue-26241-1762945462

Fix: Correct inaccurate Email as Username prerequisite for all affected versions (Product IS issue #26241)

Author: himeshsiriwardana

en/includes/guides/organization-management/organization-discovery/email-domain-based-organization-discovery.md

@@ -21,13 +21,22 @@ In this example scenario:
 - User Alice with email `[email protected]` should go to the login screen of `Best Car Mart` organization.
 - User Bob and Ben, with emails `[email protected]` and `[email protected]` should go to the login screen of `Glory Car Mart` organization.
 
+## Prerequisites
+
+Before you configure email domain-based organization discovery, understand the following requirements:
+
+### Username requirements during user creation
+
+For any user to be discoverable by their email domain, the following requirements must be met during user creation:
+
+- The user's **username** must be in a valid email format (for example, `[email protected]`).
+- The domain portion of this username (for example, `company-domain.com`) must match one of the domains configured for organization discovery.
+- This is a strict requirement during user creation. Attempting to create a user with a non-email username or a username with a non-matching domain for an organization with this feature enabled will fail.
+
 ## Enable email domain based organization discovery
 
 !!! note "Important"
     - The root organization only permits enabling this feature and mapping email domains to organizations.
-    {% if product_name == "WSO2 Identity Server" %}
-    - For this feature to work, make sure to [enable email address as the username]({{base_path}}/guides/users/attributes/enable-email-as-username/) so that users may log in to applications with their email addresses.
-    {% endif %}
     - **For Just-In-Time (JIT) provisioning**: Set the Subject Attribute to `http://wso2.org/claims/emailaddress` in your external identity provider. See [Map email domains to organizations](#map-email-domains-to-organizations) below.
 
 === "Using the Console"