A fast lightweight mail server for linux?

[therealgtron]

one of our postfix / amavis installs is now sending up to 6,000 messages per hour. it seems it can't handle the load and is failing. now we're looking for something that's fast.

any suggestions on a smtp solution that can do dkim signing, handle several thousand messages per hour? we can skip the scanning for outgoing messages because we're all about performance and avoiding failures on this box.

[lammert]

It can be failing for many reasons. Maybe there is not enough memory, maybe the CPU is too slow or maybe the disk access too slow. You first have to measure system performance before you know how to increase performance. Switching to other email software while your current installs are working fine (except for throughput) should only be a last resort.

You can use utilities like top, sar and iostat or a graphical package like munin to see where the bottleneck in your current setup is.