Email blacklist check

What an email blacklist is

An email blacklist, or DNSBL (DNS-based blocklist), is a list of IP addresses and domains that a project has linked to spam or abuse. Receiving mail servers query these lists over DNS while a message is arriving. A listing can lead to outright rejection, to the message being sent to spam, or to a higher spam score that combines with other signals.

Lists differ a lot. Some are strict and widely used. Others are small, experimental or aggressive, and many receivers do not consult them at all. A listing on one obscure list matters much less than one on a major list.

How a blacklist lookup works

The IP address is reversed and the list's zone name is appended. For the address 203.0.113.25 and a list at dnsbl.example.org, the query is:

25.113.0.203.dnsbl.example.org.  IN  A

If the name does not exist (NXDOMAIN), the IP is not listed. If it returns an address in 127.0.0.0/8, such as 127.0.0.2, the IP is listed, and the exact value says which sub-list or reason applies.

SendClean finds the sending IPs from your SPF record and checks them against SpamCop, Barracuda, PSBL and Mailspike. Spamhaus, the most widely used list, refuses queries that arrive through public DNS resolvers, so it cannot be checked reliably from a web tool. Where that applies, the scan says so and links to Spamhaus's own lookup page, which you should check manually.

How to read the result

• Not listed on every list we could query is the normal, healthy result.
• Listed means a list currently holds that IP. The scan shows which list and links to its removal page.
• Could not check means the list did not answer or refused the query. It is not a listing.
• If your mail goes through a large provider such as Google Workspace, Microsoft 365 or a bulk-email service, the sending IPs are shared and the provider manages their reputation. A listing there is not something you can fix yourself, but you can report it to the provider.

An IP can also have a poor reputation without appearing on any public list. Mailbox providers keep private reputation data on both IPs and domains, and you can only see it through tools such as Google Postmaster Tools.

Why IPs get listed

• A compromised account, website form or server sending spam without your knowledge.
• Sending to purchased, old or scraped lists, which hit spam traps and produce high bounce and complaint rates.
• A shared IP whose other users misbehave.
• Running a mail server on a residential or dynamic IP range. Some lists, such as the Spamhaus PBL, list these ranges on purpose because they are not meant to send mail directly.
• An open relay or misconfigured server that lets third parties send through it.

How to get delisted

1. Find and stop the cause first. Check for compromised mailboxes, malware, outdated plugins and forms without spam protection. Delisting without a fix usually leads to relisting.
2. Open the list's lookup page and read the stated reason. Each list has its own removal process, and some delist automatically after a period.
3. Submit the removal request with accurate details. Do not repeat requests, as that can slow things down.
4. Check also that the sending IP has valid reverse DNS (PTR) matching its hostname. Many lists and receivers treat a missing one as a bad sign.
5. Rescan after the list confirms removal.

If you use a shared IP from a mail service, contact their support rather than the list. If you want to rule out other causes, see why emails go to spam.