Experienced this yesterday once more. When opening mail I see a (in egis case a non-spam) incoming message flashing by and nowhere to be found. Not in Junk or (local) Spam. Been using Spamsieve since 2004 and since the last year seeing this occasionally.
Other spam messages also just disappear.
If you see a message briefly in the inbox, that usually means that it was moved by a different computer. The messages that Mail processes on the current Mac go directly to their destination. So I would check whether you have any other Macs or devices accessing this account that might be moving the messages.
You can use the Open Log command to see which messages SpamSieve has processed. Are the ones that you saw flash listed there? Are there any that you see in the log that are missing from Mail?
I’m not sure what this is referring to. Could you give an example?
Using mail 14.0 (3618.104.22.168.52) on Big Sur beta 9.
I figured that already. The message (according to the log) was flagged spam. But on the one computer where it’s in the log the spam message is nowhere to be found. What I meant with other messages disappearing is that when I open mail (on any of 3 Macs), i see messages appearing in the inbox, disappearing from the inbox en not showing up in either Spam or Junk (local or server-side). And so no way to train it as good.
Even if it’s in the log, it’s still possible for it to have been moved by another Mac, too. Did you check the local mailboxes on the other Macs? I recommend only having one Mac access this mail account at a time while you are troubleshooting this problem.
The Mail bug may be specific to moving to a local Spam mailbox, so you could try changing the rule to move the messages to a Spam mailbox that’s on the same account that received the message.
I recommend enabling the backup feature so that even if Mail loses future messages, you’ll still have copies of them.
So what you are saying is that this is the same thing happening as discussed above, but it has happened for multiple messages?
This happens to me when I have mail that filters through the iCloud servers. They have their own spam filtering, which is non-adjustable. Check your iCloud spam folder, and I bet you will find numerous emails there.