When I launch Mail, after enabling SpamSieve 3.0b3’s filtering, immediately get the spinning beach ball and Activity Monitor shows that Mail is not responding. Turning filtering off restores Mail. This is on my M2 Pro Mac mini.
Please send beta feedback directly to spamsieve@c-command.com. If this happens again, it would be helpful if you could record sample logs from both SpamSieve and Mail.
Hopefully, I did the sample logs correctly. E-mail sent.
There are more changes in SpamSieve 3.0.2b4 that should prevent this problem, especially if you have granted Full Disk Access.