Bulk MX blacklist checker: are your domains' mail servers on an IP blocklist?
In short: Paste domains and see each one's lowest-priority MX hosts resolved to IPv4 addresses and checked against four DNS blocklists, with the list, its reason and a lookup link for any listing. Limit: Four IPv4 DNS blocklists only; a not-listed result isn't a clean bill of health.
A bulk MX blacklist checker looks up the mail servers behind a list of domains. Paste up to 9 domains, or 30 after a free Google sign-in, per ten minutes; each row finds the lowest-priority MX hosts, resolves their IPv4 addresses and checks them against four DNS blocklists, naming the list, its reason and a lookup link when one lists. DNS only. Download the CSV.
Price: this tool is free. Checking a whole email list is from $9/mo, and the first 100 checks are free with Google, no card. Check your list free nowSee pricing
Sample result
The mail server behind acme.example is on none of the four lists queried; globex.example's is listed on one.
- MX host
- mail.globex.example
- Address
- 203.0.113.10
- List
- SpamCop
What this means for you
A listing names the list and links to its reason; a hosted provider's shared IP is the provider's to fix.
- MX hosts found for you
- Four IPv4 lists over DNS
- Silent lists shown as unclear
- Reason and lookup link; CSV out
- MX
- DNSBL
- Blocklist
By SimpleVerifier Team · Last updated
Auditing the mail servers of a domain list?
- Paste the domains here: 9 per ten minutes, or 30 after a free Google sign-in. Filter to the listed rows and download the CSV.
- Upload or paste it at /verify. Every address gets a live mailbox check, and the first 100 email checks are free with a Google sign-in, no card.
How do I check the blocklist status of many domains' mail servers?
- Paste domains, email addresses or URLs, one per line, up to 9 per ten minutes or 30 after a free Google sign-in.
- Press Check MX blocklists. Each domain's MX records are read, then the first IPv4 address of the three lowest-priority hosts is checked against four DNS blocklists, 3 domains a request. Nothing is sent to the mail servers.
- Read each row: An MX IP is listed (with the list and its reason), Not listed, Unclear when a list didn't answer, Not checked, No MX to check, or Lookup failed.
- Follow a listing's lookup link to see the list's own reason, then download the CSV.
Example
- You enter
- Three domains:
acme.example,globex.exampleandinitech.example, each with a mail server on a public IPv4 address. - You get
- Each row lists the lowest-priority MX hosts with their IPs, and comes back An MX IP is listed (with the list, its reason and a lookup link), Not listed on the four lists queried, or Unclear if a list didn't answer. Download the CSV.
- Limits
- Up to 9 domains per ten minutes without an account and 30 when signed in with Google. 3 domains a request; DNS only, IPv4 lists.
Why check the IPs behind a domain's MX?
A domain's MX records say where its incoming mail goes. If the server behind them is also the one that 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; to check a list of IPs you already have, use the bulk IP blacklist checker. This tool saves the step of finding the MX IPs first.
How is each list checked?
It uses the same DNS blocklist lookups as the IP checker: Barracuda, SpamCop, PSBL and Mailspike, each queried with a reversed-IP DNS name, as RFC 5782 describes. 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. Spamhaus ZEN isn't queried because its free terms are non-commercial.
Because third-party list servers allow low-volume use, the tool runs fewer domains than the other bulk lookups, counted over ten minutes.
What does a listing mean for me?
Read the list's reason first. Listings of a hosted provider's shared mail IP, such as a large mailbox provider's inbound server, are the provider's to fix and often don't affect your own sending, which goes out through other servers. A listing of a server that you run and 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 to do it in. A not-listed result means only that these four lists don't hold the address; other lists exist.
Who uses this tool, and for what?
- Self-hosted mail operators
- Check the inbound servers behind several domains for listings after a spam incident.
- MSPs and hosting teams
- Audit client mail servers for blocklist entries before a deliverability complaint.
- Deliverability consultants
- Add a blocklist column to a client domain audit and export it as CSV.
- Cold email teams
- Check the mail hosting behind sending domains you manage.
What can’t this tool tell you?
- Four IPv4 DNS blocklists only; a not-listed result isn't 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.
- Up to 9 domains per ten minutes without an account, 30 signed in.
Common questions
- How do I check if my mail server is on a blacklist?
- Paste your domain into a bulk MX blacklist checker like this one. It finds the mail servers' IPs and checks them against four DNS blocklists, with a lookup link for any listing.
- Is this bulk MX blacklist checker free?
- Yes. It is a free tool, with lower limits than the other bulk lookups because it queries third-party lists: 9 domains per ten minutes with no account and 30 when you sign in with Google, with no card.
- Which blocklists does it use?
- Barracuda, SpamCop, PSBL and Mailspike, over DNS. Spamhaus ZEN isn't queried because its free terms are non-commercial.
- Why does a row say Unclear?
- A list gave no trustworthy answer: it timed out, refused the query, or failed its own test entry. No listing was found, but the list's answer is unknown. Run it again later.
- Does an MX listing stop my email being delivered?
- Not necessarily. MX servers receive mail. A listing hurts outgoing mail when the same IP also sends your mail.
- Does it connect to my mail server?
- No. It only asks DNS about the addresses.
Sources
A tidy list can still be full of dead addresses.
Extracting, deduplicating and syntax checks all work on the text of an address. None of them can tell whether the mailbox exists. Only the server that hosts it can answer that, through an SMTP check, and that is what the paid product does.
- Upload the cleaned file as it is: CSVs up to 100,000 rows
- A real SMTP mailbox check on every row, with catch-all detection
- Small list? Starter at $9/mo covers 2,500 emails a month, cancel anytime
Plans from $9 a month, cancel anytime, no contract. Sign in with Google and your first 100 email checks are free, no card. The free tools stay free either way.