Typically, the first time you find out that you are blacklisted is when customers start telling you that they aren’t receiving your email.  Bounced email is the number one symptom of being blacklisted.  Unfortunately, this is finding out about the problem only after it has impacted your business.

The other way to find out if you have been blacklisted is monitoring.  MxToolbox provides active monitoring solutions for blacklisting events.  Our free IP Blacklist monitor checks your server’s IP address every 7 days to give you a general warning of blacklist issues.  Our paid subscriptions check every 4 hours and premium services check at least once an hour, up to real-time blacklist checking.  The higher the frequency of checks, the more likely you will know about being blacklisted before it becomes a customer issue.