To be clear, the Mail extension filters messages immediately, just like the plug-in. The issue is that in some cases Mail fails to send new messages to the extension, so we offer the Filter spam messages in other mailboxes workaround, which checks the inbox every n seconds. The default is 60 seconds, but you can set it to a lower number so that it checks more frequently. You can also speed up the checks by archiving older messages out of the mailboxes that are selected for filtering.
While I’m investigating ways to optimize the inbox scanning, there is another way you could set things up in order to get immediately filtering. You can set up a Mail rule that filters incoming messages with SpamSieve via AppleScript. To set this up:
- Choose Settings… from the Mail menu and click the Rules button in the toolbar.
- Click the Add Rule button.
- Change the description to Move If SpamSieve Spam.
- Change the From pop-op menu to say Every Message.
- Change the Move Message pop-up menu to say Run AppleScript.
- Next to Run AppleScript, change the No Script Selected pop-up menu to say Move If SpamSieve Spam. (The script should be pre-installed if you had been using SpamSieve 2. It’s also available for download here.)
- Now click OK to close the rule and save your changes. Mail may ask if you want to apply the rule; click Don’t Apply.
- Make sure that the Training settings are set to use the the Junk mailbox.
Note that, unlike with the old plug-in based SpamSieve rule, with the script rule Mail will keep applying the rest of the rules even if the rule marks a message as spam. So it effectively acts last, and you may want to put it at the bottom of the rule list for efficiency and to make this clear. However, I doubt this would really be a problem in your situation because you wanted a way to filter messages that were left in the inbox, anyway.