Blacklist Check

What blocklists are

When a mail server or firewall wants to know if an IP address has a bad reputation, it asks a DNS-based blocklist: special DNS zones that answer "yes, listed" for addresses reported for spam, malware or attacks. Being listed does not always mean you did something wrong — shared hosting, a compromised device on your network, or simply inheriting a previously abused address from your ISP can all land a clean operation on a list. The practical effect is real though: listed mail servers get their email rejected or spam-foldered, and some networks block listed addresses outright. This tool queries the major public lists and reports hits with any detail text the list provides. Delisting is a two-step job: fix the underlying cause first (compromised account, open relay, infected host), then request removal through each operator's process — removing without fixing just gets you relisted. Results are a point-in-time snapshot; lists change constantly.