Hi, just to let you know: I installed 3.1.2 this morning and the Mail extension started working again after months and months in which I was affected by The Bug and had to use your workaround. I’m still on 15.3.2 and hope it’ll still work when I upgrade to 15.4… Best wishes!
Good news: The fix survived the OS update and is still working. Whatever you did with 3.1.2, intended or not, it helped. 
And then it stopped working again yesterday around 6 pm…
Thanks for the report. There were no changes in 3.1.2 intended to fix this, as it seems to be an Apple issue that’s out of our control. I recommend leaving Check inboxes for new messages not sent to Mail extension enabled so that filtering isn’t interrupted if the bug pops up again.
I can now reliably and consistently reproduce situations in which the extension does and doesn’t work on my Mac. It’s very simple: If I launch Mail and SpamSieve is auto-launched, it doesn’t work. If I launch SpamSieve manually before I launch Mail, it works.
That’s very interesting. Is anyone else seeing that pattern?
I know when I was developing the extension I did a lot of testing to make sure that the extension would launch the app in case the auto-launching wasn’t working. So it seems like there must be another factor besides just whether SpamSieve is already running.
Do you have SpamSieve installed directly in the Applications folder?
Yes, it’s in the root-level Applications folder.
Addition: If everything is working fine (because I launched SpamSieve before Mail), then quit SpamSieve (but not Mail) and re-launch it, the extension stops filtering the mails.
I also tried it the other way around: If SpamSieve has been auto-launched and the extension doesn’t work, it helps to quit and re-launch mail (when auto-quitting SpamSieve is turned off): The extension will then see new emails.
It’s really consistent: If SpamSieve is already running when Mail is launched, it will work. If I launch SpamSieve while Mail is running, it doesn’t.
I pointed this out a long time ago (Apple Mail extension behavior). If SpamSieve is launched first (and in my case, stays launched) the extension works. It’s been working for me ever since. At the time, you dismissed it as coincidental.
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Thanks for the follow-up. Your original post sounded to me like simply ticking the checkbox was changing the behavior—no mention of quitting or relaunching.
In any case, now that you are both reporting the same thing I have enough information to file a new bug report with Apple.
This Keyboard Maestro macro is my new workaround. If I reduce the pause between launching SpamSieve and Mail any further, the extension does not see new emails.
For those who are interested: If I reduce the first pause, Mail does not always start properly: The receive button is greyed out, I cannot quit Mail and if I send a new mail, the main window closes and cannot be reopened. Reducing the second pause creates a Mail-relaunch-cycle of death…
I usually leave mail open, so the delay does not really bother me.
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Very clever.
You might do the same with an AppleScript. You could even add the AppleScript to the LogIn items list so that SpamSieve and Mail are launched at start-up/log-in. Or, make it into a Launch Daemon of some kind.
Apple Mail certainly has some quirks, doesn’t it?
I just changed things around a bit. This is what I did:
I also added SpamSieve to the Login Items > Open at Login list.
My reasoning is that I always want SpamSieve to be running when I use Mail, which is also normally always running. (Except for when I need to restart it because of whatever mysterious thing happens within the bowels of Mail.) So, SpamSieve now opens at Login. It also doesn’t quit when Mail quits. Thus, the only time SpamSieve should ever quit is when I mistakenly tell it to quit or quit SpamSieve for some test purpose. By removing it from the Dock, I lessen the chances for a mistake. The various SpamSieve functions are still available from the menu bar icon. There is an inherent delay in opening Mail since it’s a manual operation for me.
Not really high tech, but I guess I’ll see whether this reduces the occasional unexplained happenings with Mail.
Great ideas! I chose KM because I know it well. But I think I’ll switch to your low-tech solution: SpamSieve is lightweight so it’s okay if it’s running even when Mail isn’t – which does not happen often here. Thanks!
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