Apple Mail Plug-in Not available

I am running MacOS 14.4.1 and SpamSieve 3.0.4
SpamSieve 3.0.4 News suggests:
SpamSieve reports a better error message if Mail filtering is slow and the problem can be fixed by switching from the Mail extension to the Mail plug-in.

But I cant enable the plug-in. I tried uninstalling the plug-in but the problem persists.

I want to try this option because I am getting Apple notifications of incoming email from Apple Mail that is actually spam. Spam emails are getting directed to the Junk folder, but I would prefer to see only Apple notifications of good emails, after SpamSieve has filtered the Spam.

The plug-in is not available to you because you are using macOS Sonoma and Apple removed support for Mail plug-ins in Sonoma. However, you could turn off notification in Apple Mail and let SpamSieve notify you.