After my recent issues with maildrop and delivering mail, I got to know my
system a little better. Having scanned through the qmail-queue I noticed a
lot of messages just sitting around for days on end trying to deliver to
non-existent email boxes, in response to spammers. Some of my bigger
customers had all email set to 'bounce' and not 'delete'.
Several hundred e-mail accounts getting several thousand spams a day ended
up creating a constant flow of between 10,000 and 20,000 mail messages
"bouncing" in the qmail-queue on a daily basis.
I was getting pretty worried about the hard disks that contain my mail queue
and the /var/vpopmail/domains tree. They were dishing out between 250 - 400
(I've seen it as high as 800) transactions per second on average. After
setting vdelivermail delete on some of my bigger domains, my queue has
dropped to under 1000 messages, and iostat shows a SIGNIFICANT decrease in
disk activity during both peak and off-peak times.
I wish someone had told me about that earlier. What a great tool for
reducing unnecessary load.