Apple Mail error: The specified object was not found in the store

I have a similar problem: in my case, I get the pop-up Screen Shot 2020-10-06 at 9.41.39 AM . This started happening immediately after I upgraded from Mojave to Catalina last week - never happened with Mojave. AK is the mail account Description, and SpamSieve is working, moving messages into the AK Junk folder, as before, but this pops up spontaneously, and there is no sign of the message to which it refers. I haven’t changed the scripts, or made any other modifications to SpamSieve.

Not critical, just annoying - any help will be appreciated.

Addendum: this particular message is from a sender in SpamSieve’s BlockList. From the log:

Predicted: Spam (99)
Subject: Trade Alert: Get Your $385 Payment From Zombie Mobile Game Players
From: publications@mail.stpaulresearch.com
Identifier: Lruz1Q14le3mNw8flS/zVA==
Reason: (
    "publications@mail.stpaulresearch.com"
) matched rule <From (address) Is Equal to "publications@mail.stpaulresearch.com"> in SpamSieve blocklist
Date: 2020-10-06 09:40:36 -0500 (CDT)

Does this shed any light?

Is this an Exchange account? Do you have any rules that run AppleScripts or any other rules besides the regular “SpamSieve” one shown in Step 4?

I recommend enabling the backup feature so that no more messages go missing.

Thanks for the quick reply. Yes, it is an exchange account, and I don’t have any rules that run AppleScript except for yours (drone and regular) and I haven’t changed anything since Mojave. The only change was the upgrade to Catalina.

Could you try making the drone (remote training) rule inactive and see whether that helps? If it does, we know the problem is triggered by the drone AppleScript, and maybe there’s a way to work around it.

I think I found the problem: I have a rule to delete a whole bunch of incoming emails from addresses that won’t stop bugging me. This rule I had running BEFORE the SpamSieve rules. I neglected to add the condition to stop evaluating rules after these deletes, so when SpamSieve rules ran, the message was gone. I added the condition, and we’ll see what happens.

Interesting that I didn’t change any rules when I upgraded to Catalina, and it worked fine before…

The If Apple Mail Shows an Error When Moving Messages help page has more information about how you can troubleshoot this error.