Had a bunch of problems with the Mac yesterday. Four hours chat with Apple Support. Everything cleaned up except now Spamsieve.mailbundle is being rejected, which was never a problem before.
Installed new SpamSieve 2.9.41. Didn’t change .mailbundle rejection.
At the same time Mail is also rejecting MsgFilter’s .mailbundle.
Feels like I should re-install Mail but I don’t know if that’s possible.