While reading and testing against the doc Configure direct-delivery incoming email for self-hosted sites with mail-receiver, I noticed that one detail is missing: how Discourse handles the location of the reply-key address in an email reply.
Today I confirmed in testing (with mail-receiver) that:
- A reply works if the Discourse reply-key address is in To:.
- A reply also works if the reply-key address is only in Cc:, even if To: points to a completely different address.
- The order of recipients does not matter (To vs Cc).
- Discourse will process the reply correctly as long as the reply-key address appears anywhere in the recipient list.
Other recipients simply get a copy of the message; their own replies will only work if they also include a valid reply-key for their account.
Proposed doc addition
In the section explaining how mail-receiver processes incoming messages, add a note like this:
Note on reply-key handling
Discourse will process an incoming reply-by-email message as long as the special reply-key address (e.g.reply+abcdef123@forum.example.com) appears anywhere in the recipients list.
- The reply-key does not have to be the primary To: address.
- It may be in To, Cc, or Bcc, in any order.
- This means you can send a reply with another person’s email in To: and place the Discourse reply-key in Cc: — the reply will still be matched to the correct topic.
Other recipients will just receive a copy of the email, but their own replies will only work if they also include a valid reply-key for their account.
This would save admins and users from wondering if the reply-key must always be in the To field.