Trust beats tactics™

Reputation & monitoring

Email Blocklist Checker

Enter a domain or IPv4 address. We check it against the lists that matter, tell you which ones you are on and what each one means, and point you at the right place to fix it.

New to blocklists? Read What is an email blocklist in the Email Almanac.

How this tool works

How blocklist lookups actually happen

  1. 1

    A blocklist is a DNS zone

    Listed hosts and IPs get an A record on that zone. Everything else returns NXDOMAIN.

  2. 2

    The lookup is a normal DNS query

    For an IPv4 lookup the octets get reversed, the blocklist zone is appended, and a normal DNS A query goes out. An answer is the listing, and the answer code tells you which sub-list matched and why. Domain blocklists work the same way without the reversal.

  3. 3

    A checking service runs it

    We use a service with its own access to the lists, including Spamhaus ZEN, SBL, XBL, PBL and DBL, Barracuda, SpamCop, CBL, UCEPROTECT, SURBL and URIBL. We send it the domain or IP and keep a log of what was checked, so we can improve this tool. A check can take a few minutes.

  4. 4

    No answer is never clean

    If a check cannot finish, we say we have no answer. We never show that as clean.

What one check covers

26
domain lists
65
IP lists

Every list ends in one of three answers

  • Listed
  • Not listed
  • No answer

When to use it

Reach for it in these moments

  • A campaign started bouncing

    Run your sending IP and your domain through the checker. A fresh Spamhaus SBL or Barracuda listing usually explains it in one click.

  • You just submitted a delist request

    Re-run the check. If the entry is gone from every operator, you are clear. If it came back inside a day, the underlying cause is still active.

  • You took over a domain or IP

    An inherited listing on the previous owner's mail flow is invisible until you check, and it is the cheapest source of mystery deliverability problems on day one.

Email Almanac

  • Listed, or not sure?

    Ask a real person. The Email SOS Hotline is free help with any email problem, no pitch. Cleaning a list does not remove a blocklist listing, so if you are listed, start here.

    Ask the Email SOS Hotline

  • Keep this result

    Send it to your inbox, to share with your team or compare after a fix.

    Run a check, then email it

  • Listed or not, your list is a separate check.

    Mailbox providers judge you on who you send to. Clean your first 1,000 addresses free.

    Clean your first 1,000 free