As you may remember from past problems with joe-jobs, TTLLP still has a few (maybe only one left?) qmail servers rattling around. The comments on spam-filtering suggested a few possibilities for easing matters.
As I wrote I would, I gave spamdyke a go. Maybe the out-of-the-box configuration isn’t right for me and maybe I didn’t configure it correctly, but it only cut a bit of load down and didn’t really work for me. MagicSpam seemed like a bad idea, partly because I want to slowly move people out of Plesk, not tie them into it and I hate surrendering autonomy to black boxes.
So, I installed qpsmtpd, as suggested by the legendary Steve Kemp. I found this guide to Installing qpsmtpd on SuSE 10.0 with Plesk 8.0 helpful (even though I wasn’t installing on SuSE or Plesk) and got plugins » auth » auth_imap from the qpsmtpd wiki to get SMTP AUTH working again.
The main lines of defence on the Exim servers remain a fun mix of IP-based throttling formulae and greylisting. The Postfix ones only really use greylisting, as far as I can remember. Those servers are much older than the qmail-using one, but still seem to cope.
Have you had to step-up your anti-spam systems recently? Is qmail that much worse, or is that soon-to-be-replaced 2-year-old server simply inadequate now?