diff --git a/README.md b/README.md
index a656190..3583bbf 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,9 @@
 # pl_mail
 
-A ChRIS Plugin for sending email.
\ No newline at end of file
+A ChRIS Plugin for sending email.
+
+* rcpt: Comma separated receipients. It can be specified with `-r`, `--rcpt`, or in `[inputdir]/rcpt`
+* title: Title of the email. It can be specified with `-t`, `--title`, or in `[inputdir]/title`
+* content: Content of the email. It can be specified with `-c`, `--content`, or in `[inputdir]/content`.
+* sender: Sender of the email (default: `noreply@fnndsc.org`). It can be specified in `[inputdir]/sender`, or with `-s`, `--sender`.
+* mailserver: Mail server (default: `postfix.postfix.svc.k8s.galena.fnndsc`). It can be speicified in `[inputdir]/mailserver`, or with `-m`, `--mailserver`.
diff --git a/mail.py b/mail.py
index d6a1284..5a8b970 100644
--- a/mail.py
+++ b/mail.py
@@ -64,7 +64,7 @@ def _args_or_filename(arg, filename, err_msg):
         return f.read().strip()
 
 
-def _filename_or_args(filename, arg, err_msg):
+def _filename_or_args(arg, filename, err_msg):
     if os.path.exists(filename):
         with open(filename, 'r') as f:
             return f.read().strip()