SORBS (the Spam and Open Relay Blocking System) aggregates several sub-lists covering spam sources, open relays, open proxies and dynamic IP ranges. It has a reputation for being strict, and delisting is handled through its ticketing system.
Why an IP gets listed on SORBS
Blocklists add an IP when they see evidence of spam or abuse from it: mail hitting spam traps, a compromised server sending on behalf of a botnet, an open relay or proxy, or a sudden spike in unsolicited mail. Shared hosting and cloud IPs can also inherit a bad reputation from a previous tenant. It is used by a substantial number of mail servers, so a listing can measurably reduce delivery to those systems.
How to delist from SORBS
To delist from SORBS: first fix the underlying cause (secure the host, stop the offending mail, close any open relay or proxy), then submit a removal request through the official form:
Delisting only sticks if the root cause is fixed first. Run the full Mail Health Report to catch the SPF, DKIM, DMARC or reverse-DNS problems that often cause listings.
Frequently asked questions
How do I check if my IP is on SORBS?
Enter your mail server's IP address (or your domain) in the checker above. It queries SORBS live and tells you immediately whether the IP is listed, along with how many other blocklists list it.
How long does it take to get delisted from SORBS?
Once you have fixed the underlying issue and submitted the removal request, SORBS typically processes delisting within a few hours to a few days.
Will a SORBS listing stop my email being delivered?
It is used by a substantial number of mail servers, so a listing can measurably reduce delivery to those systems.