A DNSBL task polls major domain name service (DNS) Blacklist (DNSBL) databases for an IP or a host name you specify. If the IP or host name is found in one of the DNSBL databases an error will be flagged and if you have alerts configured, an alert will be triggered.
The technology is built on top of the Internet Domain Name System. DNSBLs publish lists of addresses linked to spamming. Most mail transport agent (mail server) software can be configured to reject or flag messages which have been sent from a site listed on one or more of these DNSBLs.
If your mail servers are included in a DNSBL database it will cause other companies to deny email delivery from your servers. It is important to know if your servers are listed in DNSBLs, so you can quickly request removal and find the root cause of the DNSBL listing.
The DNSBL task references the following authoritative blacklists:
If your mail server or IP address are detected on any of these blacklists, you may need to contact the specified blacklist directly in order to determine why your address is listed and remove the address from the list.