Ever wonder if your mail server somehow wound up in a blacklist service provider's database? I found a useful tool that can help check dozens of blacklist service databases in one feld swoop.
If you go to the DNS Stuff home page you'll find a vast array of various Web-based tools. Among the tools is a spam database lookup tool, which you can use to search numerous blacklist service providers. You enter an IP address, click submit, wait a few seconds, and view the report.
If one of your mail servers is listed in a particular blacklist service database then you will of course have to address that matter directly with that blacklist provider.