I’ve removed Spam Sieve according to the instructions in the manual. There are no rules for spamsieve. But when apple mail starts it is still looking for the app. The menu entries for Spam Sieve are still in the MESSAGE drop-down.
I can find no clists or bundles referencing Spam Sieve.
How do I remove it from Mail’s startup and the mail menus?
The Uninstalling SpamSieve instructions tell you where SpamSieve’s Apple Mail plug-in is installed. Make sure that you look in the Library folder in your home folder, not the top-level Library folder.