Bulk email domain Microsoft 365 checker: which companies on my list run on Microsoft 365?
In short: Paste email addresses and see which domains show Microsoft 365 records in DNS, including ones behind a gateway, per address, in a CSV. Limit: Reads the domain, never the mailbox: Microsoft 365 records say nothing about a particular address.
A bulk email domain Microsoft 365 checker reads the domain after the @ in each address and looks up its Microsoft 365 records in DNS: MX, autodiscover, SRV and verification records. Paste up to 100 unique domains a run, or 500 signed in. Each row says whether Microsoft 365 receives the mail. It checks the domain, not the mailbox. Download the CSV.
Split by provider? Check every address before you send.
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 whose MX record points at Microsoft 365.
- Address
- tom@globex.example
- MX
- globex-example.mail.protection.outlook.com
- Autodiscover
- autodiscover.outlook.com
What this means for you
The records show where the domain's mail is received. They say nothing about whether the mailbox exists.
- Microsoft 365 mail or behind a gateway
- Verified-only domains flagged
- Nothing sent to Microsoft
- CSV out, nothing emailed
- Microsoft 365
- Autodiscover
- CSV
By SimpleVerifier Team · Last updated
Got a list of company addresses and want to know who runs on Microsoft 365?
- Paste it above to see which domains show Microsoft 365 records, one row per address 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 find which domains on an email list use Microsoft 365?
- Paste email addresses, one per line, or upload a CSV. Addresses are found anywhere in the text, so a whole export works.
- Press Check Microsoft 365 records. Only the unique domains are sent, never the mailbox names, 25 a request: DNS queries for MX, autodiscover, SRV and verification records, nothing sent to Microsoft or the domains and nothing stored. No mail is sent.
- Read each row: Microsoft 365 mail, Microsoft 365 behind another MX, Exchange elsewhere, Verified only, or No Microsoft records.
- Filter to the segment you want, download the CSV with the records beside each address, and hand the list to the mailbox check.
Example
- You enter
- Four addresses:
jane@acme.example(MX at Microsoft 365),tom@globex.example(Microsoft 365 records, MX at a gateway),ana@initech.example(autodiscover at its own server) andbo@umbrella.example(no Microsoft records). - You get
- jane: Microsoft 365 mail. tom: Microsoft 365 behind another MX. ana: Exchange elsewhere. bo: No Microsoft records. Download the CSV.
- Limits
- Up to 100 unique domains a run without an account and 500 when signed in with Google. 25 domains a request; DNS only, nothing sent to Microsoft.
What does the check read?
DNS records for the domain after the @: its MX record, the autodiscover record and SRV name, the Microsoft verification TXT record, and the lyncdiscover, sip, enterpriseregistration and enterpriseenrollment names. Microsoft's own documentation lists these as the external records a Microsoft 365 domain uses.
An MX that points at Microsoft 365 means it receives the mail. Microsoft records with a different MX usually mean a security gateway or filter sits in front.
Why check Microsoft 365 on an email list?
The provider behind a domain affects how you set up sending and what filtering to expect, and it is a way to 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.
Verified only is the weakest row: the domain proved ownership to Microsoft once, but no other record shows it uses the service now.
What do you do with the rows?
Segment by row, and treat Microsoft 365 behind another MX as a gateway case. To see which provider runs every domain, use the bulk email provider lookup, and for the same domains without the addresses, the bulk autodiscover checker.
Before you email anyone on the list, verify the addresses.
Who uses this tool, and for what?
- Cold emailers
- Split a list into Microsoft 365 and other providers before a campaign.
- Deliverability teams
- Find gateway-protected domains that filter harder.
- Vendors
- Target companies that run on Microsoft 365.
- IT consultants
- Sort prospects by whether they use Microsoft 365.
What can’t this tool tell you?
- Reads the domain, never the mailbox: Microsoft 365 records say nothing about a particular address.
- DNS only: no tenant lookup is made at Microsoft, and no mail server is contacted.
- A domain can have the records and have moved on, or use the service with records we don't read.
- Up to 100 unique domains a run without an account, 500 signed in. Free providers such as outlook.com are read like any domain.
Common questions
- How do I find which domains on an email list use Microsoft 365?
- Paste the list into a bulk email domain Microsoft 365 checker like this one. It reads each address's domain and looks up its Microsoft 365 records in DNS.
- Is this bulk email domain Microsoft 365 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 a Microsoft 365 record tell me whether the mailbox exists?
- No. It checks the domain, not the mailbox.
- What does Microsoft 365 behind another MX mean?
- The domain has Microsoft 365 records, but its MX points elsewhere, often a security gateway or filter that passes mail on to Microsoft 365.
- What does Verified only mean?
- A Microsoft verification TXT record exists but no other Microsoft record does, so the domain verified ownership once and may not use the service now.
- Does it send an email or contact Microsoft?
- No. It sends DNS queries only. Nothing is sent to Microsoft or the domains, and no mail server is contacted.
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.