Blacklist Checker

Blacklist Checker queries an IP address against several major public email blacklists (DNSBLs) at once, the same lookup mail servers themselves perform before deciding whether to accept a message, and reports which ones currently list it.

This is the tool to reach for when outbound mail is landing in spam folders or being rejected outright and a blacklisting is a suspect, after moving to a new server or IP to confirm you have not inherited a previous tenant's bad reputation, or periodically as a health check for anything that sends real mail.

Being listed on one blacklist does not mean mail is blocked everywhere, since different providers weigh different lists differently, and delisting always has to happen directly with whichever blacklist operator listed the address, not through Frabs.