After upgrading to Mountain Lion (OS 10.8) which included Mail 6.0, I suddenly stopped getting as much mail as normal and then noticed that a ton of my “good” mail was being routed to the Spam folder (using SpamSieve 2.9.3).
Upon opening the SpamSieve application, I was presented with a pop-up whereby SpamSieve asked for permission to access my Contacts database. When granted, SpamSieve once again started recognizing everyone in Contacts (the old Address Book) as a friendly and life returned to normal on the e-mail front.
I realize this is probably a privacy measure but thought I’d mention it in case there might be a way to have SpamSieve flash a warning after the OS 10.8 upgrade and upon the first opening of Apple’s Mail 6.0 application without having to physically open the SpamSieve application.
This probably indicates that SpamSieve’s plug-in was not installed. Normally, it will stay installed when updating to Mountain Lion, but I’ve seen a few cases where the update disables it. When the plug-in is not installed, Mail will route all the messages to the Spam mailbox, without asking SpamSieve.
I don’t think the change in behavior relates to the address book prompt. A side effect of launching SpamSieve is that it will re-enable the plug-in if it had been disabled. That’s probably why things started working for you.
Starting with Mountain Lion, the OS will prompt you the first time the application tries to access the address book. There’s no way to make this happen before launching the application. However, under normal circumstances the plug-in would have been installed and Mail would have auto-launched SpamSieve as soon as you received new mail. It will ask for Contacts access before classifying any messages as spam.