In the event that you have an IP address that is listed on a blacklist you can modify your server's IPtables configuration to reroute port 25 traffic to a secondary IP.

Use the following command to modify your routing tables:

 
# iptables -t nat -A POSTROUTING -o eth0 -p tcp -j SNAT --dport 25 --to-source 1.2.3.4

Be sure to replace 1.2.3.4 with your secondary IP!

You must have a secondary IP address for this to work. If you do not you may request one by creating a ticket in your Control Panel. Please note that a new IP address will require your server to be rebooted and will have an additional charge applied to your account each month.

--Kelly Koehn 10:54, 30 October 2009 (CDT)