What a blacklist listing actually means

Seeing your IP on a blocklist is unpleasant, but the right response depends on which list it is and why you are there.

Not all lists are equal

A handful of lists are consulted by large mailbox providers and affect delivery directly. Many more are small, run by one person, or no longer maintained. We tier lists as critical, important and informational so you know where to start. A listing on an informational list rarely needs more than a note.

Why IPs get listed

• The previous owner of a new address left a bad history.
• The server was compromised or misconfigured and sent mail it shouldn't.
• Recipients complained, or the address hit a spam trap.
• Authentication or reverse DNS is missing, which some lists treat as suspicious.

What to do

1. Read the listing. Most lists say why they listed you.
2. Fix the cause. Removal without a fix leads to a quick re-listing.
3. Request removal using the list's own process. Some remove automatically after a quiet period.
4. Set up a monitor so the next listing reaches you in minutes instead of days.

Honest results

A check can fail for reasons that have nothing to do with you: a list may refuse queries from busy resolvers or time out. Our results mark those lists as errors instead of showing a false clean result, and we never report a list as listing you unless it said so.

Try the free blacklist check, or read how results are classified.