Mail Server Tweaks.

I've started to gather informations, about tweaking Mail Servers.
The test OS is a GNU/Debian 3.1.
My first attempt was Sendmail, at which I failed to disable the delay introduced
after each command, so I leave it for other time.

Next was Exim.
To see what exactly I'm testing, I do a
exim -bV
which shows the version and other good info:

"Exim version 3.36 #1 built 02-May-2005 21:51:12
Copyright (c) University of Cambridge 2002"

For start, I read http://pigtail.net/LRP/exim.html
to get a hold of the cli parameters.
After that, I've done some more reading : http://www.exim.org/exim-html-4.50/doc/html/spec.html

I was concerned about the queue, since this is the process that eats most of the resources. The thing I found first was:

"By default all these message files are held in a single directory called input inside the general Exim spool directory. Some operating systems do not perform very well if the number of files in a directory gets very large; to improve performance in such cases, the split_spool_directory option can be used. This causes Exim to split up the input files into 62 sub-directories whose names are single letters or digits."

Another issue is the extra logging, which eats up some disk access.
"The use of individual message logs can be disabled by setting no_message_logs; this might give an improvement in performance on very busy systems."


To increase the deliver speed, but not decrease the socket-sucking speed, I tried
starting exim like:

exim -bd -q1s