I have a pretty fast machine as an mta. The load and iostat are always very low but the active queue can still get pretty high. If I set $sa_local_tests_only = 1 in amavisd.conf.in there is never a problem and if the queue is high, restarting with local tests only processes the queue very quickly.
I have all the rbls turned off, I have dns caching and the performance settings from the wiki enabled.
Anyone have any ideas how to make this faster?