What is Mailspike?

If you've just spotted Mailspike in a bounce message or spam filter log, your first question is probably: "How worried should I be?" The honest answer is: it depends on who's filtering your mail, but it's worth addressing.

Mailspike runs IP-based reputation blocklists with both free and commercial tiers. What sets it apart from a simple blocklist is that it doesn't just flag IPs as "bad." It scores them on a spectrum, from actively blocked to positively reputed. That means it can hurt you or quietly help you, depending on your sending history.

The main zones you'll come across are z.mailspike.net (the combined reputation zone), bl.mailspike.net (the blocklist), and wl.mailspike.net (the whitelist, for IPs with good standing). When a receiving mail server queries Mailspike, it gets back a score, not just a yes or no.

Why does any of this reach you? Mailspike is integrated into SpamAssassin, which is used by a huge range of hosting providers, corporate mail servers, and security appliances. It's not in the same league as Spamhaus for raw reach, but because SpamAssassin is so widely deployed, a Mailspike listing can quietly push your score over the spam threshold for a meaningful number of recipients.

What typically gets you listed: spam complaints detected by Mailspike's systems, a pattern of poor sender reputation, or association with infrastructure that's been flagged for abuse.

To check your status and request removal: head to mailspike.org/lookup. Mailspike offers automated delisting for IPs that have cleaned up their act. If your sending behavior has genuinely improved, the process is usually straightforward. Persistent listings mean you probably haven't fixed the underlying cause yet.

If you're suddenly seeing delivery problems and Mailspike shows up as a factor, you can run a full blocklist check with our free Blocklist Checker to see the full picture at once. And if things are breaking right now, the SOS hotline is free.