How to Monitor IP Blocklists

If you operate outbound email services, it’s important to know when one of the IP addresses from which you send email has been listed on a blocklist. When an IP is blocklisted, delivery from the IP can be severely affected, causing a surge in customer support issues.

How to Monitor IP Blocklists

If you have only a small number of IP addresses, the are various IP blocklist monitoring services available on the web, which can monitor your IP addresses for you and send alerts when an IP becomes listed. If you have a large number of IP addresses, it becomes more cost-effective to develop an in-house monitoring solution, which can query each blocklist against each of your IP addresses.

List of the Most Important IP Blocklists

Not all IP blocklists are created equal: Some IP blocklists are far more important than others, because a larger
number of email receivers implement these blocklists as tools in their anti-spam arsenal. The following is a list of the most important IP blocklists, which you should be monitoring.

• Spamhaus – Several distinct IP reputation lists should be monitored continuously, including:
  • Spamhaus Block List (SBL) – generated from continuous anti-spam research, with human intervention
  • Exploits Block List (XBL) – mostly automated, but equally as important as the SBL
• Spam and Open Relay Blocking System – very influential
• UCEPROTECT – fully automated, and asks for payment for removal requests