improve email template

email_handler.py

@@ -1010,6 +1010,7 @@ def handle_unknown_mailbox(
     authorize_address_link = (
         f"{URL}/dashboard/mailbox/{alias.mailbox_id}/#authorized-address"
     )
+    mailbox_emails = [mailbox.email for mailbox in alias.mailboxes]
     send_email_with_rate_control(
         user,
         ALERT_REVERSE_ALIAS_UNKNOWN_MAILBOX,
@@ -1021,6 +1022,7 @@ def handle_unknown_mailbox(
             alias=alias,
             sender=envelope.mail_from,
             authorize_address_link=authorize_address_link,
+            mailbox_emails=mailbox_emails
         ),
         render(
             "transactional/reply-must-use-personal-email.html",
@@ -1028,6 +1030,7 @@ def handle_unknown_mailbox(
             alias=alias,
             sender=envelope.mail_from,
             authorize_address_link=authorize_address_link,
+            mailbox_emails=mailbox_emails
         ),
     )
 

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

@@ -8,10 +8,8 @@
   {% endcall %}
 
   {% call text() %}
-    Please note that sending from this alias only works from one of these mailboxes: <br>
-    {% for mailbox in alias.mailboxes %}
-      - {{ mailbox.email }} <br>
-    {% endfor %}
+    Please note that sending from this alias only works from alias's owning mailboxes, that are
+    {{ mailbox_emails|join(", ") }}
   {% endcall %}
 
   {% call text() %}

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

@@ -2,11 +2,8 @@ Hi {{name}}
 
 We have recorded an attempt to send an email from your alias {{ alias.email }} using {{ sender }}.
 
-Please note that sending from this alias only works from one of these mailboxes:
-
-{% for mailbox in alias.mailboxes %}
-- {{mailbox.email}}
-{% endfor %}
+Please note that sending from this alias only works from alias's owning mailboxes, that are
+    {{ mailbox_emails|join(", ") }}
 
 This is to protect against "email spoofing", i.e. someone else sending emails from your mailbox.
 If {{ sender }} can indeed send emails from your alias, you can add it to the allow list on {{authorize_address_link}}