Postfix + MySQL Performance Tricks.
There are many guides to setting up postfix using a MySQL backend. However, none of them mention performance issues.
If you run a mail server with high volume, MySQL falls flat pretty quickly. I experienced this on one of my servers for the past couple weeks. When I finally started searching for a soltuion, I found two really good techniques to minimize the number of connections that postfix will open to MySQL.
The main problem with our setup was that for each incoming connection, postfix would issue 4 queries before even accepting the message. This volume of queries is not necessarily a
Cisco VPN Client and Resolving Local Hosts.
One problem I have always had with the Cisco VPN client is that while connected it can’t resolve local hosts.
This is because it overwrites /etc/resolv.conf with the DNS server at the other end of the VPN. I cannot find an option for the pcf file to disable this behavior. However, it is easy enough to stop by doing the following.
# chattr +i /etc/resolv.conf
So, now the problem becomes resolving REMOTE hosts. This is easily solved using dnsmasq. Dnsmasq can be configured to use specific dns servers for particular domains.
# yum install dnsmasq
# chkconfig --levels 345 dnsmasq on
# echo nameserver 127.0.0.1 >>
