If you are getting hangs in Mail, please record a sample report from Mail during the hang. That will show what Mail is doing. When training from Apple Mail on High Sierra, it is actually running the exact same code as SpamSieve 2. The relevant files are untouched by the SpamSieve 3 upgrade. So this seems likely to be an issue with Mail’s data store, unrelated to SpamSieve. We’ll see in the sample.
Thanks for sending in the sample log. However, please wait until Mail is showing you the rainbow cursor and then select the Mail app in the list in Activity Monitor. The sample that you sent was from the SpamSieveLaunchAgent process.
I received another sample log from you, but it was a log of SpamSieve. Please select the Mail app in the list in Activity Monitor. We want the sample from Mail because that’s the app that you said was showing the rainbow cursor.
That said, it looks like maybe the slowness is caused because you have selected Add green flag to unread good messages and/or Including in the inbox. These are not needed with the macOS 10.13 that you are using—they are intended for testing the operation of the Mail extension on macOS 12.0 and later—so I recommend that you uncheck them.