Slow Processing Messages
If you are using the Filter spam messages in other mailboxes feature, make sure that you have not selected mailboxes with large numbers of messages, as this can slow down Mail. You can see in Settings ‣ Apple Mail ‣ Filtering which mailbox is currently being filtered to see which one might be causing the slowness. Only select mailboxes that receive new messages. If there are lots of old messages, move them to an unfiltered mailbox. You can also reduce the CPU use by setting SpamSieve to check for new mail less frequently.
Slow Launching
If Mail is launching slowly (which can cause SpamSieve to deactivate its Mail rule) and you are using macOS 10.14 or later, the slowness is probably caused by a Mail bug. After a Mail plug-in (any plug-in, not just SpamSieve) has been installed for a long time, Mail sometimes pauses before loading it. There are two ways to work around this:
Manual
Deactivate and then reactivate the plug-in:
Go to the Rules tab of Mail’s Settings and uncheck the SpamSieve rule.
Go to the General tab of Mail’s Settings and click on Manage Plug-ins…. Uncheck SpamSieve.mailbundle and restart Mail.
Note: It is important to temporarily disable the plug-in this way, from within Mail, rather than using the Uninstall Apple Mail Plug-In… command, as Mail has access to reset files that SpamSieve cannot access.
Go back to Manage Plug-ins… and check SpamSieve.mailbundle. Now restart Mail again.
Go to the Rules tab of Mail’s Settings and check the SpamSieve rule to make it active again.
This will usually speed up Mail’s launching for several months, if not longer, at which point you may need to repeat the procedure above. If you find that Mail slows down again sooner than that, please let us know.
Automatic (Experimental)
On macOS 13 and with SpamSieve 2.9.52 or later, you can click this link to tell SpamSieve to enable its automatic workaround for this issue. You can also click here to disable the workaround. Please let us know if you encounter any problems.
Hang When Launching
If Mail is not just slow (as above) but does not finishing launching at all (after waiting a few minutes), it may help to:
Hang When Training
A bug in macOS 13.1 can cause a hang when you train a message as good or as spam. To work around this, go to Mail ‣ Settings ‣ Accounts ‣ Account Information and set Download Attachments to All for each account. This fix will probably only help for new messages (received after you change the setting). If there is a particular old message that you want to train, it may help to open it in its own window and/or to use File ‣ Save As… to save it in Raw Message Source format. That can trigger Mail to finish the download. Another option is to copy the message to a different mailbox and then train the copy.
General Slowness
Reporting Slowness
If none of these suggestions helped, please see the Sending in a “Sample” Report section.