Blacklist listings block delivery to large portions of the internet. Checking and resolving them is one of the first steps when troubleshooting email deliverability problems.
How to Check
MXToolbox (Checks 100+ Blacklists at Once)
Go to mxtoolbox.com/blacklists.aspx, enter your domain or IP. Shows all listings instantly.
Spamhaus Direct Check
check.spamhaus.org — the most important single blacklist. Spamhaus listings affect Gmail, Outlook, and most corporate mail servers.
Gmail Postmaster Tools
postmaster.google.com shows your domain reputation with Gmail specifically. "Bad" here means heavy filtering even without a formal blacklist entry.
Why You Got Listed
- Spam complaint rate above 0.1–0.3%
- Spam trap hits
- Purchased or harvested lists
- Sudden volume spike from new domain
- Compromised sending infrastructure
Delisting Process
- Spamhaus: Online removal form at spamhaus.org/removal. Fix the issue first, then request.
- Barracuda: barracudacentral.org/rbl/removal-request — can be nearly instant.
- Microsoft: Use Microsoft's sender support portal.
Critical: Fix the underlying problem before requesting delisting. Re-listing with a pending request makes future requests harder.
Prevent blacklisting — build reputation with proper email warmup →