And it seems that SpamAssassin does not analyze them. Or it is only this way on my end, and it differs by yours?
I'm not sure.
This is what happens on my end. SpamAssassin Bayes is a very slow learner. I have a SpamAssassin Bayes database that I have taught over time. I set up the user's SpamAssassin, then I delete the new Bayes and copy in mine. That's a huge head start for them. From there, the user fine tunes with TeachIsSpam and TeachIsNotSpam. When they teach using the inter-server messages, they never hear from them again. However, spammers have a daily rotation of a new name and place from which to send spam from. The reason I said I'm not sure in the beginning, is normally SpamAssassin Bayes kills them even if they haven't heard of them before, and under these conditions it doesn't seem to be anymore effective than blocking by the source, which of course changes every day.
On the desktop side, nothing beats POPFile. However, POPFile only works well on POP3, which does nothing for you mobile devices, and their IMAP plugin proved limited, and more trouble than it was worth. One thing some users have done is setting up Outlook with POP3 and IMAP for the same account. They use the consolidated POP3 inbox with its superior POPFile E-Mail classification, and view and teach the IMAP side where they can view what was lassoed by SpamAssassin, and teach based on what got lassoed by POPFile, to keep it off their phone. Spam and Trash get cleaned by cron after the time period you set.
On the mobile side, I haven't found the equivalent of POPFile for POP E-Mail, and mobile devices are so vulnerable to getting lost or trashed you wouldn't want that to be your only record of E-Mails anyway, so only IMAP makes sense there. It also allows them to teach Bayes and check the on-server spam folder. I haven't proven any Anti-Spam highly effective for mobile IMAP yet, but admittedly I haven't spent a lot of time experimenting.
Other:
The output queue doesn't look bad for frozen messages, but then it shouldn't. There is one user that seems like a common recipient. I went to his Maildir and there are few things that I don't understand with what I see that you may be able to help me with. In the Maildir directory structure for the vUser:
- There is nothing unusual about Maildir/.Drafts, Maildir/.INBOX.*, Maildir/.Sent, Maildir/.Trash, or Maildir/Junk E-mail.
- Maildir/cur is 2.5GB. I assume is his Inbox. However, I really don't see any crap in stored in there.
- I'm not getting any messages about too many E-Mails sent by anyone.
So the bottom line is I'll look at it as another spam problem to solve.
Thanks!