If you use a Plesk server as your outgoing SMTP to send email from your client (I like Thunderbird!) you may notice that it takes FOR-EVER to connect and send. After a quick Google search, I found out that you need to disable reverse DNS lookup to speed things along. This page is where I found the fix and it has great info. I’ll dupe it here for the hell of it.
Edit your /etc/xinet.d/smtp_psa (and smtps_psa for secure connetions I assume). Under “server_args” insert “-Rt0” after the equals sign.
Before:
server_args = /var/qmail/bin/relaylock /var/qmail/bin/qmail-smtpd /var/qmail/bin/smtp_auth /var/qmail/bin/true /var/qmail/bin/cmd5checkpw /var/qmail/bin/true
After:
server_args = -Rt0 /var/qmail/bin/relaylock /var/qmail/bin/qmail-smtpd /var/qmail/bin/smtp_auth /var/qmail/bin/true /var/qmail/bin/cmd5checkpw /var/qmail/bin/true
Restart xinetd via /etc/init.d/xinetd restart
and you’re done! Test it out, your SMTP should be much faster.