Cloudflare + Microsoft 365: SPF, DKIM and DMARC setup that passes

If your Microsoft 365 mail is landing in spam, or someone is sending invoices as your domain, the cause is almost always the same three records — published wrongly, published twice, or never published at all. This guide fixes that for a domain whose DNS lives at Cloudflare.

What each record does

Three records, three separate jobs. Publishing one and assuming you are covered is the usual reason mail still lands in spam.

Since 2024 Gmail and Microsoft both expect all three from anyone sending at volume. A missing DMARC record alone is now enough to affect placement.

Step 1 — Find the DNS editor and lower the TTL

In Cloudflare: Dashboard → select domain → DNS → Records → Add record

Leave TTL on Auto — Cloudflare serves it at 300 seconds, which is already what you want. TTL is how long resolvers cache a record — at four hours, a typo takes four hours to correct everywhere; at five minutes it is effectively reversible. Put it back once everything passes.

Step 2 — Audit what is already there

List every record of type TXT and write down anything starting with v=spf1.

• Zero SPF records — straightforward; you add one in step 3.
• Exactly one — you will edit it, not add another.
• Two or more — already broken, and the most common state we find. Step 3 fixes it by merging.

Note any include from a previous host. Whether you keep it comes down to one question: does that server still send mail for you? A website contact form or WooCommerce order notification counts. If nothing sends from there any more, drop it.

Step 3 — Publish exactly one SPF record

Add a new record in Cloudflare with these values:

Cloudflare accepts @ or the bare subdomain and shows you the resulting full name below the field. Read it before saving. Content goes in unquoted. Cloudflare will not accept line breaks.

If you also send from your website or another service

Merge, never duplicate. One record, one v=spf1 at the start, one ~all at the end, every include in between:

v=spf1 include:spf.protection.outlook.com include:othersender.example ~all

Keep the total number of DNS-resolving mechanisms — every include:, a:, mx: and redirect= — at ten or fewer. Above ten, SPF returns a permanent error and fails as though absent.

Why ~all rather than -all? Softfail marks unlisted senders as suspicious; hardfail rejects them outright. Start with ~all and tighten once DMARC reports confirm nothing legitimate is being missed. Never use +all — it authorises the entire internet to send as you.

Step 4 — Generate the DKIM key in Microsoft 365

This half happens in Microsoft 365, not Cloudflare. Go to Microsoft Defender portal → Email & collaboration → Policies & rules → Threat policies → Email authentication settings → DKIM.

1. Select your domain in the DKIM list and click Create DKIM keys.
2. Microsoft shows two CNAME targets — copy both; DKIM here needs two records, not one.
3. Each target looks like selector1-yourdomain-com._domainkey.yourtenant.onmicrosoft.com.
4. Publish both CNAMEs before returning to the portal.

Leave that tab open — you come back to it in step 5, and forgetting to is the second most common failure.

Add the DKIM records in Cloudflare

Use the bare host as shown — not the full selector1._domainkey.yourdomain.com, for the same reason as the SPF record. If the value is rejected as too long, remove any line breaks your clipboard introduced; it must be one continuous string.

Step 5 — Switch signing on (the step everyone forgets)

Once both CNAMEs resolve, go back to the DKIM page and switch Sign messages for this domain with DKIM signatures to Enabled. Microsoft refuses to enable it until both records are visible.

The two selectors rotate keys automatically — never delete one because it looks unused. If enabling fails, the usual cause is a typo in the tenant part of the target, which is easy to mistype and impossible to spot at a glance.

Step 6 — Publish DMARC in monitoring mode

Back in Cloudflare, one more record:

Start at p=none. It enforces nothing, but it starts the aggregate reports arriving, and those reports are how you find the sender you forgot about — the invoicing tool, the CRM, the old newsletter platform.

Resist going straight to p=reject. On a domain with a forgotten sender, reject means those messages vanish silently, and the first you hear of it is a client asking why they never got your quote.

Step 7 — Verify, then tighten

Wait fifteen minutes, then check all three. From a terminal:

dig yourdomain.com TXT +short
dig selector1._domainkey.yourdomain.com CNAME +short
dig _dmarc.yourdomain.com TXT +short

Or run the domain through our record checker, which flags duplicates and weak policies for you. For an end-to-end test, send a message to a Gmail address you own, open it and use Show original — you want PASS beside SPF, DKIM and DMARC.

The tightening schedule

• Week 1–2: leave p=none and read the reports. Identify every legitimate sender.
• Week 3: add missing senders to SPF (merged into the one record), then move to p=quarantine.
• Week 5+: if reports stay clean, move to p=reject and change SPF to -all.
• Finally: restore the TTLs.

A note on MX records

Microsoft's MX is yourdomain-com.mail.protection.outlook.com at priority 0, with your domain's dots replaced by hyphens. Also publish the autodiscover CNAME to autodiscover.outlook.com so Outlook configures itself.

Authentication cannot fix a routing problem. If mail is not arriving at all — as opposed to arriving in spam — the MX records are where to look first, not SPF.

When it still does not work

Mail still in spam with all three passing

Authentication is necessary, not sufficient. Check your domain and sending IP against a blocklist, make sure you are not mailing purchased lists, and give a brand-new domain a few weeks of low-volume sending before expecting good placement.

Microsoft 365 says the DKIM record cannot be found

Nine times out of ten the host field contains the domain twice. Open the record in Cloudflare and confirm it reads exactly selector1._domainkey and selector2._domainkey.

SPF was fine, then broke after adding a service

That service told you to "add this SPF record" and you added a second one. Merge them into one.

DMARC reports arrive as unreadable XML

They are meant to — the format is for machines. Paste one into any free DMARC report analyser, or point rua at a reporting service that renders them for you.