[FIX] mail: less confusing To: header for mailing-list posts

Many mail clients will replace the name in the To:
header with Me if the To: email matches the email
of the user. These users will see To: Me instead of
"Followers of ..." and usually believe this was a
private email from the sender to them.
But when replying they would reply to the whole list.

Fix this by explicitly forcing the To: to be the
mailing list address.

addons/mail/mail_group.py

@@ -221,12 +221,13 @@ class mail_group(osv.Model):
     def message_get_email_values(self, cr, uid, id, notif_mail=None, context=None):
         res = super(mail_group, self).message_get_email_values(cr, uid, id, notif_mail=notif_mail, context=context)
         group = self.browse(cr, uid, id, context=context)
-        res.update({
-            'headers': {
-                'Precedence': 'list',
-            }
-        })
+        headers = res.setdefault('headers', {})
+        headers['Precedence'] = 'list'
         if group.alias_domain:
-            res['headers']['List-Id'] = '%s.%s' % (group.alias_name, group.alias_domain)
-            res['headers']['List-Post'] = '<mailto:%s@%s>' % (group.alias_name, group.alias_domain)
+            headers['List-Id'] = '%s.%s' % (group.alias_name, group.alias_domain)
+            headers['List-Post'] = '<mailto:%s@%s>' % (group.alias_name, group.alias_domain)
+            # Avoid users thinking it was a personal message
+            # X-Forge-To: will replace To: after SMTP envelope is determined by ir.mail.server
+            list_to = '"%s" <%s@%s>' % (group.name, group.alias_name, group.alias_domain)
+            headers['X-Forge-To'] = list_to
         return res

openerp/addons/base/ir/ir_mail_server.py

@@ -415,6 +415,13 @@ class ir_mail_server(osv.osv):
         smtp_to_list = filter(None, tools.flatten(map(extract_rfc2822_addresses,[email_to, email_cc, email_bcc])))
         assert smtp_to_list, "At least one valid recipient address should be specified for outgoing emails (To/Cc/Bcc)"
 
+        x_forge_to = message['X-Forge-To']
+        if x_forge_to:
+            # `To:` header forged, e.g. for posting on mail.groups, to avoid confusion
+            del message['X-Forge-To']
+            del message['To'] # avoid multiple To: headers!
+            message['To'] = x_forge_to
+
         # Do not actually send emails in testing mode!
         if getattr(threading.currentThread(), 'testing', False):
             _test_logger.info("skip sending email in test mode")