On the official Mailman FAQ site it is stated: I didn't have a concurrencyremote file in /var/qmail/control (I have the RPM build) Adding that file did not help. I sent an announcement email to 100K email addresses (validated and bona fide). I used both EZMLM and Mailman. Both programs filled up the mail queue and delivery was quite slower than on a Plesk 5 box that I moved from. I now have Plesk 8 and 2 GB more RAM than on my Plesk 5 box.... Is it possible that Qmail is doing DNS resolution on recipients for messages delivered locally? Is there a fix for this? Is there a way to use qmail-inject?