Speed up SMTP on Debian/Plesk servers
on Monday 7th April, 2008 Gabe speculated thusly…I recently found that sending emails via my server was painfully slow. After further invesitigation in to this issue I discovered that the server was performing reverse-DNS checks on client IPs. These were slow because they often didn’t work and had to wait for a timeout. The solution is to turn of reverse-DNS checking on the server by editing a config file as follows…
The modification must be made to the /etc/inetd.conf file:
smtp stream tcp nowait root /path/to/qmail/bin/tcp-env tcp-env -Rt0 ...
smtps stream tcp nowait root /path/to/qmail/bin/tcp-env tcp-env -Rt0 ...
It is necessary to restart inetd in order for the changes to take effect:
# kill -HUP `cat /var/run/inetd.pid`
Note, /etc/inetd.conf may be overwritten and the options you added will be removed if you make certain changes through Plesk CP, for example add MAPS server.