How to Find Email Addresses With No Mail Server in a List

To find email addresses with no mail server, take the domain after the @ in each address and ask DNS for its MX records. A domain with none, or with a null MX, cannot take mail, so every address there will bounce. The bulk email domain MX checker does this for a pasted list or CSV, up to 1,000 unique domains a run (5,000 after a free Google sign-in), and gives every address a row.

It checks the domain, not the mailbox. That is the limit to keep in mind through the whole post.

Why lists hold addresses at dead domains

Old signups, mistyped forms, purchased lists and companies that closed or let a domain lapse all leave addresses behind that can never receive mail. Finding them by domain is cheap, because a list of thousands of addresses usually has far fewer unique domains.

The by-hand way

1. Copy the domain from an address, for example acme.example from sam@acme.example.
2. Look up its MX records with the MX lookup.
3. No MX records? Look up its A record. RFC 5321 tells a sending server to fall back to it.
4. Neither? Mail to every address at that domain will bounce.

That works for one domain. For a list, see bulk DNS lookup for a list of domains.

Step 1: paste the addresses

Paste addresses one per line, or upload a CSV. They are found anywhere in the text, so a whole export works. Only the unique domains are sent, never the mailbox names, 100 a request.

Step 2: run the check

Press Check mail servers. No mail is sent and no mail server is contacted.

Step 3: read the result

Result	What it means
Has a mail server	The domain has MX records
No MX, address record only	Mail can still arrive by the fallback rule, but real mail setups almost always have MX. Look at these
Accepts no mail (null MX)	The domain says it never takes mail (RFC 7505)
No mail server	Neither MX nor an address record. Every address bounces
DNS didn't answer	A timeout. Run the list again

Filter to the dead-domain rows, download the CSV and remove them. To see who hosts mail on the good domains, use the bulk email provider lookup, and read what a null MX is.

What this check cannot do

• It never opens a connection to a mail server, so it says nothing about any person's address.
• A domain with a healthy MX can hold mailboxes that were closed years ago, and a catch-all domain accepts everything.
• Only MX records and, when there are none, the address record are read.
• The limit is 1,000 unique domains a run without an account and 5,000 signed in.

For why these bounces matter, see hard bounce vs soft bounce.

Next: confirm the addresses exist

Removing dead domains is the cheap first pass. The domains that remain still hold closed mailboxes, and only the mailbox check asks the mail server about each address. Upload it at the verify page: a Google sign-in gets you the first 100 email checks without a card. The result per address is valid, risky or invalid plus the reason, with no email sent to anyone. If the list is large or comes back every month, see bulk email verification.

Check your list now

Paste it into the bulk email domain MX checker.