If your email is suddenly bouncing or landing in spam, the first thing to rule out is a blacklist (DNSBL) listing — a record that flags your sending IP as a source of spam. The blacklist check tests your mail servers against the major lists at once. Here's how, using google.com as the example.

Step 1 — Enter an IP or domain

On the blacklist check, enter either a mail server's IP address or a domain. Give it a domain and it resolves that domain's MX servers to their IPs and checks each one. Press Check blacklists.

Blacklist check form with a domain entered and the Check blacklists button
Enter an IP or a domain and press Check blacklists. (click to enlarge)

Step 2 — Read the result

Each sending IP is queried against five major blocklists in parallel:

  • 1The LISTINGS count is the headline — 0 means you're clean on every list checked.
  • 2Every mail server IP gets a Clean (5/5) verdict (or a listing) across Spamhaus ZEN, Barracuda, SpamCop, SORBS, and PSBL — shown row by row so you know exactly which list flagged you.
Blacklist result showing zero listings, the resolved mail server IP marked Clean 5 of 5, and each of the five DNSBLs reporting Not listed
Zero listings, with each IP checked against five DNSBLs — a clean bill of health. (click to enlarge)

What to do if you're listed

A listing usually means a compromised account, a misconfigured server, or a shared IP someone else abused. Fix the underlying cause first — lock down any compromised account, make sure your authentication (SPF, DKIM & DMARC) is solid, and confirm your reverse DNS is set — then use the delisting form on the specific blocklist that flagged you. For the wider picture of deliverability problems, see why are my emails going to spam?