Bulk autodiscover checker: which domains have Microsoft 365 set up in DNS?
In short: Paste domains and read the DNS records Microsoft 365 asks customers to publish: autodiscover, the MS= verification TXT, the Teams (Skype for Business) and Intune CNAMEs, and whether the MX points to Exchange Online. Limit: Reads published records only; stale records can remain after a company leaves Microsoft 365.
A bulk autodiscover checker reads the DNS records Microsoft 365 asks each customer domain to publish. Paste up to 100 domains or email addresses, or 500 after a free Google sign-in, and each row shows the autodiscover record and where it points, the MS= verification TXT, Teams and Intune records, and whether the MX goes to Exchange Online. It finds Microsoft 365 behind a gateway. DNS only. CSV out.
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
globex.example's mail goes to a security gateway, but autodiscover points to autodiscover.outlook.com.
- Domain
- globex.example
- MX
- mx1.gateway.example
- autodiscover
- autodiscover.outlook.com
What this means for you
Behind the gateway, the mailboxes are most likely Microsoft 365.
- autodiscover CNAME and SRV
- MS= verification TXT
- Teams and Intune records
- Finds Microsoft 365 behind gateways
- Autodiscover
- Microsoft 365
- Exchange
By SimpleVerifier Team · Last updated
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Segmenting a lead list by Microsoft 365?
- Microsoft 365 tenants filter cold email hard, and bounces make it worse. Upload the list at /verify to remove addresses that would bounce, including on Microsoft 365 domains behind a gateway.
- The first 100 email checks are free with a Google sign-in, no card. For every provider, not only Microsoft, use the bulk email provider lookup.
How do I check autodiscover for many domains?
- Paste domains or email addresses, one per line, up to 100 a run or 500 after a free Google sign-in.
- Press Check autodiscover. Each domain gets eight DNS queries (autodiscover CNAME and SRV, TXT, MX, and the Teams and Intune names), 25 domains a request.
- Read each row: Microsoft 365 mail, Microsoft 365 behind another MX, Exchange elsewhere, Verified only or No Microsoft records, with every record found.
- Filter by result and download the CSV.
Example
- You enter
- Three domains:
acme.example(MX at Exchange Online),globex.example(MX at a gateway, autodiscover at autodiscover.outlook.com) andinitech.example(no Microsoft records). - You get
- acme.example: Microsoft 365 mail. globex.example: Microsoft 365 behind another MX. initech.example: No Microsoft records. Each row lists every record found. Download the CSV.
- Limits
- Up to 100 a run without an account and 500 when signed in with Google, counted over a minute. 25 domains a request; DNS only.
Which records does the checker read?
The ones in Microsoft's external DNS records for Microsoft 365: the autodiscover CNAME (to autodiscover.outlook.com for Exchange Online) and the _autodiscover._tcp SRV record, the MS=ms TXT record that proves a domain was added to a tenant, the MX record (to mail.protection.outlook.com), lyncdiscover and sip for Teams and Skype for Business, and enterpriseregistration and enterpriseenrollment for Intune device sign-up.
Outlook uses autodiscover to set itself up from just an address and password, as Microsoft describes. A record that points anywhere other than Microsoft usually means an on-premises Exchange server or a host's own autodiscover service.
What do the results mean?
Microsoft 365 mail: the MX goes to Exchange Online. Microsoft 365 behind another MX: autodiscover or the Teams records point to Microsoft, but the MX goes elsewhere, usually a security gateway such as Proofpoint or Mimecast in front of Exchange Online. Exchange elsewhere: autodiscover exists but points to another server. Verified only: just the MS= TXT record, so the domain was added to a tenant but may not use its mail. No Microsoft records: none of these were found.
Records can outlive their use: a company that moved to Google Workspace may still have an old autodiscover CNAME. The row lists every record so you can judge.
Why does Microsoft 365 behind a gateway matter?
Most provider lookups read only the MX, so a domain behind Proofpoint looks like Proofpoint. The mailboxes, and the filtering that decides the inbox, are often still Microsoft's. Knowing that helps you follow Microsoft's sender requirements and choose which inboxes to send from.
Everything is read from public DNS. Nothing is sent to Microsoft or to the domains' servers.
Who uses this tool, and for what?
- Cold emailers
- Find Microsoft 365 domains hidden behind Proofpoint or Mimecast before choosing sending inboxes.
- IT consultants
- Audit a client's domains for missing or stale autodiscover and Teams records.
- Sales teams
- Build a list of companies on Microsoft 365 for a Microsoft-related offer.
- Migration teams
- Check which domains still point autodiscover at an old Exchange server.
What can’t this tool tell you?
- Reads published records only; stale records can remain after a company leaves Microsoft 365.
- Can't see the tenant's name or licences, which aren't in DNS.
- Microsoft's Teams and Intune records are optional, so many real tenants don't publish them.
- Up to 100 domains a run without an account, 500 signed in.
Common questions
- How do I check if a list of companies uses Microsoft 365?
- Paste their domains into a bulk autodiscover checker like this one. It reads the autodiscover, MS= TXT, Teams, Intune and MX records Microsoft 365 uses and labels each domain, with a CSV.
- Is this bulk autodiscover checker free?
- Yes. Up to 100 domains a run without an account, and up to 500 a run when you sign in with Google, with no card.
- What is the autodiscover record?
- A DNS record, usually a CNAME at autodiscover.yourdomain, that Outlook and other mail apps use to find the mailbox server. For Microsoft 365 it points to autodiscover.outlook.com.
- What does the MS=ms TXT record mean?
- It is the value Microsoft asks for when a domain is added to a Microsoft 365 tenant, to prove ownership. It shows the domain was verified, not that it still uses Microsoft mail.
- Can these records be out of date?
- Yes. DNS records stay until someone removes them, so a company that left Microsoft 365 can still have them. The MX shows where mail goes today.
- Does the tool contact Microsoft?
- No. It only reads public DNS records. Nothing is sent to Microsoft's servers or the domains' mail servers.
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.