[IMP] mass_mailing: add unsubscribe headers in mailing emails

Globally a backport of odoo/odoo@c0775de where mail sent through
mass mailing now have unsubscribe headers set. This requires a small update
in the send method to allow email-specific headers; previously to this commit
only generic headers from the mail.mail were considered.

With some fixes, notably csrf is disabled on unsubscribe route as it is now
called directly as one-click, without form and csrf. This is necessary notably
to allow famous email readers to include links directly in their UI.

Task-3932001 (Mail: Unsubscribe Headers Everywhere)

addons/mail/models/mail_mail.py

@@ -342,6 +342,16 @@ def _send(self, auto_commit=False, raise_exception=False, smtp_session=None):
                 # build an RFC2822 email.message.Message object and send it without queuing
                 res = None
                 for email in email_list:
+                    # support headers specific to the specific outgoing email
+                    if email.get('headers'):
+                        email_headers = headers.copy()
+                        try:
+                            email_headers.update(email.get('headers'))
+                        except Exception:
+                            pass
+                    else:
+                        email_headers = headers
+
                     msg = IrMailServer.build_email(
                         email_from=mail.email_from,
                         email_to=email.get('email_to'),
@@ -356,7 +366,7 @@ def _send(self, auto_commit=False, raise_exception=False, smtp_session=None):
                         object_id=mail.res_id and ('%s-%s' % (mail.res_id, mail.model)),
                         subtype='html',
                         subtype_alternative='plain',
-                        headers=headers)
+                        headers=email_headers)
                     processing_pid = email.pop("partner_id", None)
                     try:
                         res = IrMailServer.send_email(

addons/mass_mailing/controllers/main.py

@@ -27,7 +27,9 @@ def unsubscribe_placeholder_link(self, **post):
         """Dummy route so placeholder is not prefixed by language, MUST have multilang=False"""
         raise werkzeug.exceptions.NotFound()
 
-    @http.route(['/mail/mailing/<int:mailing_id>/unsubscribe'], type='http', website=True, auth='public')
+    # csrf is disabled here because it will be called by the MUA with unpredictable session at that time
+    @http.route(['/mail/mailing/<int:mailing_id>/unsubscribe'], type='http', website=True, auth='public',
+                csrf=False)
     def mailing(self, mailing_id, email=None, res_id=None, token="", **post):
         mailing = request.env['mailing.mailing'].sudo().browse(mailing_id)
         if mailing.exists():

addons/mass_mailing/models/mail_mail.py

@@ -82,14 +82,27 @@ def _send_prepare_body(self):
     def _send_prepare_values(self, partner=None):
         # TDE: temporary addition (mail was parameter) due to semi-new-API
         res = super(MailMail, self)._send_prepare_values(partner)
-        base_url = self.env['ir.config_parameter'].sudo().get_param('web.base.url').rstrip('/')
-        if self.mailing_id and res.get('body') and res.get('email_to'):
+        if self.mailing_id and res.get('email_to'):
+            base_url = self.mailing_id.get_base_url()
             emails = tools.email_split(res.get('email_to')[0])
             email_to = emails and emails[0] or False
+
             unsubscribe_url = self._get_unsubscribe_url(email_to)
-            link_to_replace = base_url + '/unsubscribe_from_list'
-            if link_to_replace in res['body']:
-                res['body'] = res['body'].replace(link_to_replace, unsubscribe_url if unsubscribe_url else '#')
+
+            # replace links in body
+            if f'{base_url}/unsubscribe_from_list' in res['body']:
+                res['body'] = res['body'].replace(
+                    f'{base_url}/unsubscribe_from_list',
+                    unsubscribe_url,
+                )
+
+            # add headers
+            res.setdefault("headers", {}).update({
+                'List-Unsubscribe': f'<{unsubscribe_url}>',
+                'List-Unsubscribe-Post': 'List-Unsubscribe=One-Click',
+                'Precedence': 'list',
+                'X-Auto-Response-Suppress': 'OOF',  # avoid out-of-office replies from MS Exchange
+            })
         return res
 
     def _postprocess_sent_message(self, success_pids, failure_reason=False, failure_type=None):