Set up DMARC on Microsoft 365

You want a DMARC record on Microsoft 365, and what that comes down to is one TXT record at the host _dmarc under your domain, holding a short policy string that begins v=DMARC1.

Microsoft 365 runs the mailboxes for the domain. It has no DMARC switch anywhere in its own settings, and the DMARC record is added wherever the domain’s DNS lives, which may or may not be Microsoft.

The record comes first on this page, with what each part of it means, and the exact Microsoft 365 fields it goes into come after, because the record is the same wherever your DNS lives and only the form around it changes.

The record before the console

DMARC is the instruction a receiver reads after it has checked SPF and DKIM on a message claiming to come from your domain. Those two checks each return a pass or a fail. DMARC tells the receiver what you want done with a fail, and where to send a summary of what it saw. The instruction lives in DNS because that’s the one place a receiver anywhere in the world can look up something only the domain’s owner can write.

The host is _dmarc, with the _ character at the front, and the type is TXT. The value to start with is:

v=DMARC1; p=none; rua=mailto:[email protected]

Three tags carry the meaning. v=DMARC1 names the version of the standard and has to come first. p= is the policy: none asks receivers to deliver failing mail as they would have anyway and report on it, quarantine asks them to put failing mail in spam or junk, and reject asks them to refuse it during delivery. rua=mailto: names the mailbox that receives the aggregate reports, which arrive as XML attachments listing which servers sent mail as your domain and whether each one passed.

A message passes DMARC when SPF or DKIM passes and the domain that passed matches the domain in the From header. That matching is called alignment, and it’s why a mail provider’s own SPF record isn’t enough on its own: the check has to succeed for your domain, since that’s the one the reader sees.

Other tags turn up in records elsewhere. sp= sets a separate policy for subdomains and defaults to whatever p= says; the subdomain policy piece covers when it’s worth setting. pct= applies the policy to a share of failing mail. adkim= and aspf= switch alignment from relaxed to strict, and ruf= asks for per-message forensic reports, which most large receivers don’t send. Leave all of these out at the start; the three-tag record above is complete and valid.

Start at p=none. Publish p=reject before you know your SPF and DKIM pass on your own mail and you’ll bounce your own invoices along with the forgeries. The reports are how you find that out, so the rua= address has to be a mailbox somebody opens.

Check that Microsoft 365 answers DNS for the domain

Check the Nameservers section in the registrar account to see which company answers DNS for the domain. If Microsoft 365 is the DNS host, the record goes in the Microsoft 365 admin center under Settings, then Domains, then DNS records. If another company runs the nameservers, the record goes in that company’s DNS settings instead, usually under a menu labelled DNS, Records, or Advanced DNS.

Microsoft 365 publishes nothing for DMARC on its own. The record is typed into the DNS records page, and Microsoft’s only role is hosting that DNS records page when Microsoft happens to run the domain’s nameservers.

Publish SPF and DKIM before DMARC. The policy tells receivers what to do when those checks fail, so a domain with neither has nothing for DMARC to work from, and a p=reject on such a domain refuses everything that carries its name.

Add the record in the Microsoft 365 console

1. Sign in to the DNS host, which is the Microsoft 365 admin center only if Microsoft runs the domain’s nameservers.
2. Open the domain’s DNS settings, usually labelled DNS, Records, or Advanced DNS.
3. Add a new record and choose the record type TXT.
4. In the Name or Host field, enter exactly _dmarc, keeping the leading _ character.
5. Do not type _dmarc.yourdomain.com in that field, since the DNS host appends the domain automatically.
6. In the Value or Content field, paste v=DMARC1; p=none; rua=mailto:[email protected], replacing the email address with a mailbox that is read.
7. Paste the value unquoted, since most DNS hosts add the surrounding quoting themselves.
8. Leave the TTL field at the host’s default setting.
9. Save the record so it publishes.

The type field takes TXT. The Name or Host field takes _dmarc exactly, with the leading _ character and nothing appended, since the DNS host adds the domain itself. The Value or Content field takes the full record string starting v=DMARC1;, pasted without surrounding quotes. The TTL field stays at whatever default the host offers.

Look for an existing TXT record at _dmarc before you add one. A domain gets one DMARC record, and a receiver that finds two treats the domain as having none, so if one is already there you edit it. Paste the value without surrounding quotation marks and without a trailing space or line break, then compare the last few characters against the record above once it’s saved.

Traps in the Microsoft 365 form

• There is no DMARC toggle inside Microsoft 365. Searching the admin centre’s own settings for a DMARC option finds nothing, because the record lives in DNS, not in a mailbox setting.
• Leaving off the _ character in _dmarc, or typing the full domain after it, puts the record at the wrong host name and the DMARC check will not find it.
• Exactly one TXT record should exist at _dmarc. Where one is already present, edit it rather than adding a second.
• A DMARC record published before SPF and DKIM are working can get the domain’s own legitimate mail blocked once the policy tightens beyond p=none.
• The rua address must be a mailbox that someone reads, otherwise the reports arrive nowhere.

A record that’s present and malformed is worse than an absent one in a single respect: it looks done. v=DMARC1 missing from the front, p= misspelt or left out, a rua= without mailto: in front of the address, or curly quotes pasted in from a document all produce a record receivers can’t parse and so ignore. The DMARC typos piece lists the ones that show up most often in the census.

With those checked and the record saved, run the free scan below. It looks up _dmarc on your domain the way a receiving mail server does and tells you whether the record is present, whether it parses, and which policy it carries.

Wait, then read the result

Once saved, the change can take from minutes up to a couple of hours to be visible everywhere. The saved record appears back in the same DNS records list it was added to, whether that list sits in the Microsoft 365 admin center or in another provider’s DNS settings.

A scan run in the first minutes after saving can read as absent while nothing is wrong, because a resolver somewhere is still handing out its cached answer from before the record existed. If the scan still reports no DMARC after a couple of hours, go back to the nameserver check at the top of this page first and the host name second.

A record saved into a console that isn’t answering DNS for the domain is the most common reason a scan comes back unchanged, and the fix is to add the same record at the company the nameservers point to.

When the scan shows the record and its policy, you’re in the monitoring stage. Nothing about delivery has changed yet, and the first reports take a day or so to arrive.

Tightening from none to reject

p=none leaves delivery as it was and starts the reports arriving. Those reports are the only evidence you’ll get about what sends as your domain: your mail provider, a newsletter tool, an invoicing system, and whatever else somebody connected two years ago. Each report names the sending server, how many messages it sent, and whether SPF and DKIM passed for them. The DMARC piece explains how to read one and what a failing row means.

Without a record, a receiver that sees a message fail both checks has no instruction from you, so most deliver it anyway and nobody tells you. Of the 316,600,902 domains carrying a grade in the September 2026 census, 238,156,049 (75.2%) have no DMARC record at all. The monitoring stage has its own trap: of the domains whose DMARC record carries p=none, 33,651,068 (80.33%) have no rua= address, so they sit at none collecting nothing that would let them move.

Read the reports until every sender you recognise is passing and the failing rows are ones you don’t. Then change p=none to p=quarantine in the same field you saved it in, wait for a further round of reports to confirm your own mail still lands, and change it to p=reject. That last edit is the one that turns a monitoring record into an instruction receivers act on, and it takes the same minute in the Microsoft 365 console as the first one did.

Figures as of 5 September 2026, from the September 2026 edition of the defaults.exposed census. Census numbers move every month; the current values are on the census data page.