emails: Remove referrer name from 'From' header in invitation emails.

We should only show the referrer name in subject of invitation emails,
and show only 'Zulip' in the 'From' header. This helps in preventing
the email from being marked as suspicious by the detection systems
when they see an employee's name as sender of an email sent from an
unrelated domain.

The behavior is already the same for reminder invitation emails where
we do not show name and only 'Zulip' in the 'From' header.

Fixes #18256.

zerver/lib/actions.py

@@ -6480,11 +6480,9 @@ def do_send_confirmation_email(invitee: PreregistrationUser, referrer: UserProfi
         "activate_url": activation_url,
         "referrer_realm_name": referrer.realm.name,
     }
-    from_name = f"{referrer.full_name} (via Zulip)"
     send_email(
         "zerver/emails/invitation",
         to_emails=[invitee.email],
-        from_name=from_name,
         from_address=FromAddress.tokenized_no_reply_address(),
         language=referrer.realm.default_language,
         context=context,

zerver/tests/test_signup.py

@@ -928,9 +928,7 @@ https://www.google.com/images/srpr/logo4w.png</a></p>"""
 
 
 class InviteUserBase(ZulipTestCase):
-    def check_sent_emails(
-        self, correct_recipients: List[str], custom_from_name: Optional[str] = None
-    ) -> None:
+    def check_sent_emails(self, correct_recipients: List[str]) -> None:
         from django.core.mail import outbox
 
         self.assert_length(outbox, len(correct_recipients))
@@ -939,8 +937,7 @@ class InviteUserBase(ZulipTestCase):
         if len(outbox) == 0:
             return
 
-        if custom_from_name is not None:
-            self.assertIn(custom_from_name, self.email_display_from(outbox[0]))
+        self.assertIn("Zulip", self.email_display_from(outbox[0]))
 
         self.assertEqual(self.email_envelope_from(outbox[0]), settings.NOREPLY_EMAIL_ADDRESS)
         self.assertRegex(
@@ -987,7 +984,7 @@ class InviteUserTest(InviteUserBase):
         invitee = "alice-test@zulip.com"
         self.assert_json_success(self.invite(invitee, ["Denmark"]))
         self.assertTrue(find_key_by_email(invitee))
-        self.check_sent_emails([invitee], custom_from_name="Hamlet")
+        self.check_sent_emails([invitee])
 
     def test_newbie_restrictions(self) -> None:
         user_profile = self.example_user("hamlet")
@@ -1274,7 +1271,7 @@ class InviteUserTest(InviteUserBase):
         invitee = f"Alice Test <{email}>"
         self.assert_json_success(self.invite(invitee, ["Denmark"]))
         self.assertTrue(find_key_by_email(email))
-        self.check_sent_emails([email], custom_from_name="Hamlet")
+        self.check_sent_emails([email])
 
     def test_successful_invite_user_with_name_and_normal_one(self) -> None:
         """
@@ -1288,7 +1285,7 @@ class InviteUserTest(InviteUserBase):
         self.assert_json_success(self.invite(invitee, ["Denmark"]))
         self.assertTrue(find_key_by_email(email))
         self.assertTrue(find_key_by_email(email2))
-        self.check_sent_emails([email, email2], custom_from_name="Hamlet")
+        self.check_sent_emails([email, email2])
 
     def test_can_invite_others_to_realm(self) -> None:
         def validation_func(user_profile: UserProfile) -> bool:
@@ -2230,7 +2227,7 @@ class InvitationsTestCase(InviteUserBase):
         prereg_user = PreregistrationUser.objects.get(email=invitee)
 
         # Verify and then clear from the outbox the original invite email
-        self.check_sent_emails([invitee], custom_from_name="Zulip")
+        self.check_sent_emails([invitee])
         from django.core.mail import outbox
 
         outbox.pop()
@@ -2261,7 +2258,7 @@ class InvitationsTestCase(InviteUserBase):
         error_result = self.client_post("/json/invites/" + str(9999) + "/resend")
         self.assert_json_error(error_result, "No such invitation")
 
-        self.check_sent_emails([invitee], custom_from_name="Zulip")
+        self.check_sent_emails([invitee])
 
     def test_successful_member_resend_invitation(self) -> None:
         """A POST call from member a account to /json/invites/<ID>/resend
@@ -2278,7 +2275,7 @@ class InvitationsTestCase(InviteUserBase):
         prereg_user = PreregistrationUser.objects.get(email=invitee)
 
         # Verify and then clear from the outbox the original invite email
-        self.check_sent_emails([invitee], custom_from_name="Zulip")
+        self.check_sent_emails([invitee])
         from django.core.mail import outbox
 
         outbox.pop()
@@ -2309,7 +2306,7 @@ class InvitationsTestCase(InviteUserBase):
         error_result = self.client_post("/json/invites/" + str(9999) + "/resend")
         self.assert_json_error(error_result, "No such invitation")
 
-        self.check_sent_emails([invitee], custom_from_name="Zulip")
+        self.check_sent_emails([invitee])
 
         self.logout()
         self.login("othello")
@@ -2329,7 +2326,7 @@ class InvitationsTestCase(InviteUserBase):
                 invitee, ["Denmark"], invite_as=PreregistrationUser.INVITE_AS["REALM_OWNER"]
             )
         )
-        self.check_sent_emails([invitee], custom_from_name="Zulip")
+        self.check_sent_emails([invitee])
         scheduledemail_filter = ScheduledEmail.objects.filter(
             address__iexact=invitee, type=ScheduledEmail.INVITATION_REMINDER
         )