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Query 90+ DNSBLs for an IP or mail domain.
The Blacklist Check queries 90+ DNS-based block lists (DNSBLs) for an IP address or mail domain, reporting which lists flag it so you can identify and resolve the reputation problem causing mail delivery failures.
Enter an IP address (203.0.113.10) or a mail domain and run the tool. The probe checks the address against every major public block list.
Input: IP or domain — e.g. 203.0.113.10.
Each line shows a block list and whether the address is LISTED or CLEAR, with the return code if listed. Listings on lists like Spamhaus SBL, XBL or PBL are the most common cause of mail being rejected by recipients. Follow the list's delisting procedure for each one that flags you.
→ Find which block lists are flagging a mail server IP.
→ Diagnose sudden mail delivery failures after a reputation drop.
→ Check an IP before assigning it to a new mail server.
→ Verify delisting succeeded after resolving a listing.
Spamhaus SBL lists spam sources and botnets; XBL lists compromised/hijacked hosts and open proxies; PBL lists dynamic/non-mail-sending IP ranges (ISP end-user pools). A PBL listing is expected for residential IPs and is fixed by sending mail through your ISP’s smarthost, not by delisting.
Visit the list’s website (linked in the return code) and follow its delisting process — usually a form confirming the issue is resolved. Fix the root cause (open relay, compromised account, spam) first, or you will be relisted quickly.
Receivers use many reputation signals beyond DNSBLs — content filters, sender reputation, engagement, and private blocklists. A clean DNSBL result rules out one cause but does not guarantee inbox placement.