Messages not threading in smart mailbox

Is “View ▸ Organize by Thread” enabled for the Today mailbox?

(Sorry about the late reply.)

It is. (And no worries about the reply delay.)

This is new to me. Are no messages threaded in the Today mailbox? Or is it just some messages?

You can enable the “Msg ID” column in the messages outline to make sure that these really are the same messages. (Just in case the two messages are not parent-child in the Today mailbox -- MailMate is very strict about threading.)

It looks to be all messages that don't get threaded. In the case of the two I'm looking at right now, they have different Msg IDs. However, MailMate is identifying them as threaded in the thread arcs. I'm attaching another screenshot. In this case, it's the messages "Eiusmod Labore" and "Laboris Aute" that aren't getting threaded in the smart mailbox, but you can see that there's a thread arc showing. They again get threaded in a different smart mailbox (second screenshot).

FYI, I procrastinated some of this testing (I've been using a LOT of email clients simultaneously after Apple f'd Mail.app), so I'm running out of trial days. I'll try to keep on top of this ticket so I can get you answers before I run out.

What I meant with respect to Msg ID was to make sure that it was the same two messages which are shown in one mailbox as in the other mailbox - but this appears to be the case (based on date). And you are absolutely sure “View ▸ Organize by Thread” is enabled for both mailboxes?

Maybe send me the following file and then perhaps I can try to reproduce the problem (“Help ▸ Send Feedback” if you like). So far it makes little sense:

~/Library/Application Support/MailMate/Mailboxes.plist

(Currently, you can still use MailMate after the trial runs out. It's just a hassle if you send more than two messages per day.)

Sending screenshots of the tree folders with Organize by Thread enabled (this time the messages are "Officia Dolore" and "Officia Aute;" sorry they keep changing, but I have to process a lot of email for my job). You can see they have the same IDs in all mailboxes. I'm also attaching my Mailboxes.plist.

I cannot reproduce it, but now I think I noticed something. Based on the spacing in front of each field in the messages outline, it appears you do not have an outline column (the one with triangles). Could you try right-clicking the headers of the messages outline and look for “Outline Column”. Does it make a difference if you change this setting?

Unfortunately, that didn't do anything, either.

But was an outline column missing for the Today mailbox? I don't know how the mailbox could get into such a state and maybe that is related to the threading problem (note that I have no other reports about this type of threading problem and therefore I'm looking for some kind of seemingly unrelated trigger).

Thanks for your patience.

An outline column wasn't missing. HOWEVER! I switched the outline column around for a while, and then restarted MailMate, and this problem is now fixed. So, it seems like that was the cause, somehow? Anyway, thanks so much for taking the time to help me!