How to Find Which Email Addresses on a List Use Microsoft 365

To find which email addresses on a list use Microsoft 365, look up the MX, autodiscover and verification records of the domain after the @ in each address. The bulk email domain Microsoft 365 checker does this for every address in a pasted list or CSV and gives each one a row.

The check reads the domain, not the mailbox.

Why check this on an email list

The provider behind a domain affects how you set up sending and what filtering to expect, and it lets you segment a list for provider-specific campaigns. A list of thousands of addresses has far fewer unique domains, so one set of lookups per domain is cheap.

The by-hand way

1. Take the domain after the @, for example acme.example from sam@acme.example.
2. Query its MX record, for example dig MX acme.example, and see whether it ends in mail.protection.outlook.com.
3. Query autodiscover.acme.example and the Microsoft verification TXT record.
4. Compare them, and repeat for every unique domain.

For a plain list of domains, see check if a domain uses Microsoft 365.

Step 1: paste the addresses

Paste addresses one per line, or upload a CSV. Only the unique domains are sent, never the mailbox names.

Step 2: run the check

Press Check Microsoft 365 records. The DNS queries are made from our server. Nothing is sent to Microsoft or the domains, and no mail is sent.

Step 3: read the result

Result	What it means
Microsoft 365 mail	The MX record points at Microsoft 365
Microsoft 365 behind another MX	Microsoft records exist but the MX is elsewhere, often a gateway
Exchange elsewhere	Autodiscover exists but doesn't point at Microsoft 365
Verified only	Only a verification TXT record, no other Microsoft record
No Microsoft records	None found

The CSV carries the MX, autodiscover and verification columns beside each email. No address is left out of the list handed on to the mailbox check.

What this check cannot do

• It checks the domain, not the mailbox.
• DNS only: no tenant lookup is made at Microsoft.
• A domain can have the records and have moved on.
• Up to 100 unique domains a run without an account, 500 signed in.

To see which provider runs each domain, use the bulk email provider lookup.

Next: the rest of the list

For the addresses that remain, use the verify page: the first 100 checks are free with a Google sign-in, no card.

Try it now

Paste your list into the bulk email domain Microsoft 365 checker at simpleverifier.com.