Sometimes a dog shakes just to lose a few fleas. Works for dropping spammers from mail servers, too. Now and then, just issue a new IP address, then watch your firewall logs for SMTP rejections at the old IP address. We’re pleasantly suprised every time we do it.

Last time changed a mail server’s IP address, we spotted a lot of SMTP rejections in a cluster of IPs: 216.219.109.184, 216.219.109.188, 216.219.109.192, 216.219.109.193, 216.219.109.197, 216.219.109.198, 216.219.109.199, 216.219.109.200, 216.219.109.205, 216.219.109.213, 216.219.109.214, 216.219.109.224, 216.219.109.225.

After using Black List Check and Whois, we discovered that all of the IPs belonged to PactWeb, Estrategies and Squib Networks. Interestingly, all three share the same address: 222 Rte 9W, PMB 257,Haverstraw,NY 10963. In addition, while the names of the nameservers were unique, like ns1.pactweb.com, ns1.estrategics.com, ns1.squibnetworks.com, the IPs were the same: 64.28.67.198 and 64.28.67.199.

A Whois of these IP addresses yielded a bounty of additional domains: BOOLEVER.COM, CRYSTALHOLDINGS.COM, WINSOMGROUP.COM, BOOLEANSTRATEGIES.COM, PROPERHIT.COM, TOUCHMETRICS.COM, and CENTERUNION.COM. (You can round up all related addresses related by registering at Whois Source. PactWeb alone has 86 domains listed, including pactde.com, pactlm.com and pactmn.com.) We adjusted our blacklist accordingly.

Here’s the checklist for changing your mail server’s IP:

  • Change your mail server IP address in its Network Settings;
  • Change your mail server IP address at the Domain Name Server;
  • Set your firewall to reject SMTP to the old IP, and;
  • Set your firewall to allow SMTP to the new IP.

Is shaking off a few fleas worth the effort? Only your dog… and your mail server… knows for sure.

Next: Found: A Nest of Email… Marketers?