notify user if reply from alias is NOT sent from their personal email

app/email_utils.py

@@ -143,6 +143,31 @@ def send_cannot_create_domain_alias(user, alias, domain):
     )
 
 
+def send_reply_alias_must_use_personal_email(user, alias, sender):
+    """
+    The reply_email can be used only by user personal email.
+    Notify user if it's used by someone else
+    """
+    send_email(
+        user.email,
+        f"Reply from your alias {alias} only works with your personal email",
+        _render(
+            "reply-must-use-personal-email.txt",
+            name=user.name,
+            alias=alias,
+            sender=sender,
+            user_email=user.email,
+        ),
+        _render(
+            "reply-must-use-personal-email.html",
+            name=user.name,
+            alias=alias,
+            sender=sender,
+            user_email=user.email,
+        ),
+    )
+
+
 def send_email(to_email, subject, plaintext, html):
     if NOT_SEND_EMAIL:
         LOG.d(

email_handler.py

@@ -50,6 +50,7 @@ from app.email_utils import (
     send_cannot_create_directory_alias,
     send_cannot_create_domain_alias,
     email_belongs_to_alias_domains,
+    send_reply_alias_must_use_personal_email,
 )
 from app.extensions import db
 from app.log import LOG
@@ -301,6 +302,12 @@ class MailHandler:
                 reply_email,
             )
 
+            send_reply_alias_must_use_personal_email(
+                forward_email.gen_email.user,
+                forward_email.gen_email.email,
+                envelope.mail_from,
+            )
+
             send_email(
                 envelope.mail_from,
                 f"Your email ({envelope.mail_from}) is not allowed to send email to {reply_email}",

templates/emails/reply-must-use-personal-email.html

@@ -0,0 +1,8 @@
+Hi {{name}} <br><br>
+
+We have recorded an attempt to reply from your alias <b>{{ alias }}</b> from <b>{{ sender }}</b>. <br><br>
+
+Please note that reply from alias only works from your personal email ({{user_email}}): no one else could reply on behalf of your alias. <br><br>
+
+Best, <br>
+SimpleLogin team.

templates/emails/reply-must-use-personal-email.txt

@@ -0,0 +1,8 @@
+Hi {{name}}
+
+We have recorded an attempt to reply from your alias {{ alias }} from {{ sender }}.
+
+Please note that reply from alias only works from your personal email ({{user_email}}): no one else could reply on behalf of your alias.
+
+Best,
+SimpleLogin team.