Bulk email domain MX hosts checker: how many mail servers does each domain on my list have?
In short: Paste email addresses and see each domain's MX hosts with primary and backup roles, null MX and broken hosts flagged, in a CSV. Limit: Reads the domain, never the mailbox: an MX record says nothing about a particular address.
A bulk email domain MX hosts checker reads the domain after the @ in each address and queries its MX records in DNS, then checks that each mail host resolves. Paste up to 100 unique domains a run, or 500 signed in. Each row shows the hosts with primary or backup roles and flags a null MX. It checks the domain, not the mailbox. Download the CSV.
MX hosts in order? The mailbox is a separate check. Check every address.
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
tom@globex.example is at a domain with a primary and a backup MX host.
- Address
- tom@globex.example
- Primary
- mx1.mail.example (10)
- Backup
- mx2.mail.example (20)
What this means for you
More than one host keeps mail flowing. It says nothing about whether the mailbox exists.
- Primary and backup roles
- Null MX flagged
- Broken hosts flagged
- CSV out, nothing emailed
- MX
- Priority
- CSV
By SimpleVerifier Team · Last updated
Got a list of company addresses and want to see how each domain receives mail?
- Paste it above to read each domain's MX hosts and roles, with null MX domains flagged in 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 MX hosts for the domains on an email list?
- Paste email addresses, one per line, or upload a CSV. Addresses are found anywhere in the text, so a whole export works.
- Press Check MX hosts. Only the unique domains are sent, never the mailbox names, 10 a request: MX queries in DNS, then the A, AAAA and CNAME records of each MX host, nothing sent to the domains and nothing stored. No mail is sent.
- Read each row: More than one MX host, One MX host, MX problem, Null MX: takes no mail, No MX records, or Lookup failed.
- Remove the null MX rows, check the MX problem rows by hand, download the CSV with the hosts beside each address, and hand the rest to the mailbox check.
Example
- You enter
- Four addresses:
jane@acme.example(two MX hosts at different priorities),tom@globex.example(one MX host),ana@initech.example(a null MX) andbo@umbrella.example(an MX host that is an alias). - You get
- jane: More than one MX host, with primary and backup roles. tom: One MX host. ana: Null MX: takes no mail. bo: MX problem. Download the CSV.
- Limits
- Up to 100 unique domains a run without an account and 500 when signed in with Google. 10 domains a request; DNS only. A null MX domain is left out of the list handed on to the mailbox check.
What does the check read?
The MX records of the domain after the @, then the A, AAAA and CNAME records of each MX host, in DNS only. The lowest preference number is the primary, equal numbers are shared primaries and higher numbers are backups, as RFC 5321 describes.
A domain whose MX is a single dot publishes a null MX (RFC 7505), which says it takes no mail. An MX host that is an alias or an IP address is flagged as a problem.
Why check MX hosts on an email list?
A null MX or a broken MX host means mail to every address at that domain will bounce, so the whole domain can come off the list at once. A list of thousands of addresses has far fewer unique domains, so one lookup per domain is cheap.
One MX host is not a fault in itself, because most hosted providers run many servers behind one name.
What do you do with the rows?
Drop the null MX rows, look at the MX problem rows, and keep the rest. To see which provider runs each domain's mail, use the bulk email provider lookup, and for the plain yes or no on mail records, the bulk email domain MX checker.
Before you email anyone on the list, verify the addresses.
Who uses this tool, and for what?
- Cold emailers
- Remove every address at a domain that takes no mail.
- Deliverability teams
- Spot lead-list domains with broken MX hosts before a send.
- Agencies
- See how each prospect's domain receives mail.
- Developers
- Triage a signup export for domains with unusable mail setups.
What can’t this tool tell you?
- Reads the domain, never the mailbox: an MX record says nothing about a particular address.
- DNS only: no connection is made to any mail server, so a host that resolves may still refuse mail.
- A domain with no MX can still receive mail at an address record (RFC 5321), so No MX records is a flag, not a verdict.
- Up to 100 unique domains a run without an account, 500 signed in. Free providers such as gmail.com are read like any domain.
Common questions
- How do I check the MX hosts of every domain on an email list?
- Paste the list into a bulk email domain MX hosts checker like this one. It reads each address's domain, queries its MX records in DNS and checks that each host resolves.
- Is this bulk email domain MX hosts checker free?
- Yes. It is a free tool: up to 100 unique domains a run with no account, and up to 500 a run when you sign in with Google, with no card.
- Does an MX record tell me whether the mailbox exists?
- No. It checks the domain, not the mailbox.
- What is a null MX?
- An MX record that is a single dot. RFC 7505 defines it as a domain saying it accepts no mail, so mail to any address there will bounce.
- Is one MX host a problem?
- No. Many hosted providers run several servers behind one MX name. The row says One MX host so you can see it, not to flag a fault.
- Does it send an email to the domain?
- No. It sends DNS queries only and never connects to a mail server.
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.