How to Check Whether a Domain's Mail Servers (MX IPs) Are on a Blocklist

To check whether a domain's mail servers are blocklisted, find the IPs behind its MX records and look each one up on DNS blocklists. The bulk MX blacklist checker does both steps: paste up to 9 domains, or 30 after a free Google sign-in, per ten minutes. It checks the first IPv4 address of the three lowest-priority MX hosts against four lists and names the list, its reason and a lookup link when one lists. Nothing is sent to the mail servers.

Why check the IPs behind MX

A domain's MX records say where its incoming mail goes. If the same server also sends the domain's mail, which is common for self-hosted mail and small hosting plans, a blocklist entry for its IP can make outgoing mail bounce or land in spam. Domain blocklists and IP blocklists are separate. To check the domains themselves, use the bulk domain blacklist checker. For a list of IPs you already have, use the bulk IP blacklist checker.

Doing it by hand

dig +short MX example.com
dig +short A mx1.example.com
dig +short 10.113.0.203.bl.spamcop.net

For the IP 203.0.113.10 you reverse the four numbers, put them in front of the blocklist's zone name and query for an A record. An answer, normally in 127.0.0.0/8, means listed; no answer means not listed. That reversed-IP convention is described in RFC 5782. Each list publishes its own zone name and usage terms, and you repeat the query for each list.

Step 1: paste the domains

Paste domains, email addresses or URLs, one per line, up to 9 per ten minutes without an account or 30 signed in. The limit is lower than the other bulk tools because third-party list servers allow only low-volume use.

Step 2: run the check

Each domain's MX records are read, then the first IPv4 address of the three lowest-priority hosts is checked against Barracuda, SpamCop, PSBL and Mailspike, 3 domains a request. Each list's own test entry is queried too, so a list that answers wrongly or not at all shows as unclear, never as clean.

Step 3: read each row

Result	What it means	What to do
An MX IP is listed	The list, its reason and a lookup link are shown	Read the list's reason; see below
Not listed	None of the four lists holds the IP	Nothing to fix
Unclear	A list gave no trustworthy answer	Run again later
Not checked	The address was skipped	Check the IP separately
No MX to check	The domain has no MX records	Nothing to check
Lookup failed	DNS did not answer properly	Try again later

What a listing means for you

Read the list's reason first. A listing of a hosted provider's shared mail IP, such as a large mailbox provider's inbound server, is the provider's to fix and often does not affect your own sending, which goes out through other servers. A listing of a server you run that sends your mail is yours to fix: find the cause, close it, then use the list's removal page. See how to get off a blacklist for the order, and checking whether an IP address is blacklisted for single IPs.

What this check cannot do

• Four IPv4 DNS blocklists only; not listed is not a clean bill of health.
• The first IPv4 address of each of the three lowest-priority MX hosts, and no IPv6.
• A hosted provider's shared MX IP is the provider's to fix.

Check the addresses you send to

Correct DNS gets mail to the door; the address still has to exist. Upload your list on the verify page: the first 100 email checks are free with a Google sign-in, no card. Each address comes back valid, risky or invalid with a reason, and nothing is sent to anyone on the list. For larger or recurring lists, see bulk email verification, list cleaning and pricing.

Check your domains now

Paste them into the bulk MX blacklist checker.