Correct In-Reply-To: and Message-ID: MIME headers

Hi. It seems that discourse set In-Reply-To header to non-existent Message-ID.
For example, I have email for first post in topic with such headers:

Message-ID: <>
In-Reply-To: <topic/>

And a reply post to this topic has such headers:

Message-ID: <>
In-Reply-To: <topic/>

In-Reply-To from the second message must match Message-ID from the first message to let email clients correctly merge messages in threads.

Any thoughts how to fix this or whether we need it or not?

I can’t speak on that front - I’m not experienced enough with SES to know whether this is a problem with our config, or whether it’s a problem with Discourse itself.

I can say that if we want to work as a replacement for mailing lists, proper threading within email clients is a must. So yes, I think we need it.

There’s discussion of this here:

It looks like they changed the Message-ID header for this to work properly, but SES is stomping on it. This behavior is confirmed here:

Message-ID (Note: Amazon SES overrides any Message-ID header you provide.)

I guess the only way to fix this would be to switch our transactional email platform?

While I agree, I’ve never seen this problem. I wonder if it’s only an Outlook problem.

Probably, unless we can find a workaround. As I said above, it might be Outlook-only, it wfm on Thunderbird and Postbox. If that’s the case, we’d have to figure out if it’s worth it to replace a known good (other than this) part of our infrastructure. I personally don’t think it is, because this looks like a fringe case.

@m_khvoinitsky, what client are you using where threading is an issue?

Claws Mail

@tanner - can you make sure this is filed in JIRA and to link back the JIRA issue here?