Threading broken in Apple Mail on the Mac and in iOS

[adamengst (Adam C. Engst)]

Some time ago there was a discussion of threading being broken in Apple Mail.

Mac Mail Threading

Yes, sigh, I know, again. 1.7 breaks the workaround we had for Mac Mail threading, namely always including “Re:” at the start of the subject Setting for email subject Re: [%{site_name}] %{optional_pm}%{topic_title} Unfortunately, Discourse 1.7 sensibly does not include an “In-Reply-To” on the first post, and this results in the first post being threaded separately from the replies in Mac Mail. I have a hack to put the “In-Reply-To” back: @message.header['Message-ID'] = incoming_mes…

One of my users just reported this as having changed on our site, since we switched recently from SendGrid to Amazon SES.

Discourse topic openers separate from replies

@cwilcox

A topic-starting message from 5/31, when threading still worked contains this:

Message-ID: <topic/8883@talk.tidbits.com>

While my message starting this topic has this:

Message-ID: <0100016b6b37a230-92ef9d2a-ded7-43f2-b9a8-e5b9e574cf2e-000000@email.amazonses.com>

which doesn’t match the Message-ID references found in these headers in your reply:

 In-Reply-To: <topic/9031@talk.tidbits.com>
 References: <topic/9031@talk.tidbits.com>

My guess this is the problem. I think all the replies remain threaded because they all contain matching References. Topic-starting messages don’t contain a References header. If Amazon SES can avoid replacing Message-IDs or if Discourse can include a self-referential References header in topic-starting messages, the problem could go away.

I think this is a problem in Mail because it tries to be an old-school (proper) mail agent, using headers like this for threading, while Gmail is “dumb” and just uses the Subject.

It would seem that the problem is related to the Message-ID header being different. It doesn’t seem that it’s possible to override Message-ID on SES:

Amazon SES header fields - Amazon Simple Email Service

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

Any other thoughts about how I might be able to get threading to work for my users relying on Apple Mail (which is most of them)?

@peternlewis. are you still having issues here? What email service are you sending through?

[codinghorror (Jeff Atwood)]

@adamengst

since we switched recently from SendGrid to Amazon SES.

I believe Amazon SES messes with mail headers as I recall, in a particularly invasive way.

Ah yes I see you found that as well.

[peternlewis]

@adamengst

@peternlewis. are you still having issues here? What email service are you sending through?

I use my own mail server (which has its own problems, but messing with the heads is not one of them).

[adamengst (Adam C. Engst)]

Good to know. And using your own email server is enabling the threads to be maintained in Mail?

We’ve also noticed that breaking some messages out into a new topic runs into the same problem in Mail—the new topic continues to be threaded with the old one. We’re not sure why that’s happening yet.

Discourse topic openers separate from replies

[peternlewis]

@adamengst

Good to know. And using your own email server is enabling the threads to be maintained in Mail?

Yes.

Mail threading is a bizarre black box, so “works most of the time” seems to be as good as it gets.