Qmail doesn't scale well with large injection rates. Qmail
scaling in that sort of manner is completely dependant upon
the filesystem. Now this may have changed, but not that long
back everything in submission was in one dir, processing in
another dir, just like sendmail (by default) does. This
caused the queue manager to stuff up something wicked at high
injection rates.

Hans Reiser would argue that that reflects a limitation of the
filesystem, rather than of qmail; and that apps should not
have to code around such unreasonable filesystem limitations.
And reiserfs goes to considerable effort to achieve good
performance on directories containing thousands of small

This would imply that if you're going to use qmail in a high-volume
environment, you might consider using reiserfs, also.

Jim Shankland

I'd recommend also tracking/testing reiser4 in your testbed - the early
benchmarks on it are quite astounding....