Set up DKIM on Cloudflare

Setting up DKIM on Cloudflare comes down to two moves: get the selector and the public key from whoever runs your mailboxes, then publish that key as a DNS record wherever your domain’s DNS is answered. The record comes first on this page because a person who can read one can tell a good paste from a broken one.

Cloudflare is the DNS host for the domain, not the mailbox provider. The mail platform, Google Workspace, Microsoft 365 or whoever runs the mailboxes, generates the DKIM key in its own admin console, and Cloudflare only publishes the record the mail platform hands over.

What DKIM proves, and where the key has to live

DKIM (DomainKeys Identified Mail) puts a signature on each message sent from your domain. The mail platform signs with a private key it keeps to itself. The receiving server pulls the selector out of the DKIM-Signature header, looks up <selector>._domainkey.yourdomain.com in DNS, and checks the signature against the public key it finds there. A match tells the receiver two things: the message came from a system holding your private key, and nobody changed the body or the signed headers on the way.

That lookup is why the record goes where your DNS lives. Receivers don’t ask your mail platform for the key, and they don’t ask your registrar unless it happens to run the zone. They ask whichever nameservers your domain delegates to, and only the copy held there counts. The DKIM guide covers the check from the receiver’s side; this page covers the publishing side.

Two parties share the record and neither can do the other’s part. The mail platform generates the key pair inside its own console, keeps the private half, signs outgoing mail with it, and hands you the public half plus a selector. The DNS host publishes what you paste and has no way to invent a value that would verify.

Cloudflare publishes exactly the record entered in the Add record form and nothing beyond it. It does not generate, store or rotate the DKIM key itself, and it appends the domain to whatever is typed in the Name field, which is the one piece of the record it supplies on its own.

The record, tag by tag

Most platforms hand you a TXT record. Its value is a short run of tags separated by semicolons, and a typical one begins v=DKIM1; k=rsa; p= followed by the key. v=DKIM1 names the version and, when present, has to come first. k=rsa names the key type; k=ed25519 exists, and a platform that supports it will say so. p= carries the public key itself, hundreds of characters of base64 with no spaces, and it’s the one tag a receiver insists on.

Three optional tags matter. t=y marks the key as testing, so receivers treat a failed signature as if the message carried none. t=s says the identity in the signature has to be your domain itself, with no subdomain in front of it. h=sha256 limits the hash to the algorithm receivers use anyway.

Start with the value as your platform issued it, character for character, and don’t tidy it. Once mail is flowing, tighten in two places. If t=y is present, remove it so a failure counts as a failure. If the platform offers a 2048-bit key alongside a 1024-bit one, pick 2048, since it’s the length platforms now issue by default and receivers accept it.

Rotation stays the platform’s job: when it issues a new key under a new selector, you publish the new record and leave the old one up until nothing signs with it any more.

Some platforms give you a CNAME instead. The name is still <selector>._domainkey, and the target is a host on the platform’s own servers that holds the TXT value, which lets the platform rotate keys without you touching DNS again. If you were given a CNAME, publish a CNAME. Converting the target into a TXT record publishes a hostname where receivers expect a key.

The selector is the half people underrate. A receiver builds its lookup from the s= tag in the header, so the name you publish has to match the one the platform signs with, letter for letter. selector1 and selector2 are different keys, and so are mail and mail1. For DMARC alignment the d= in the signature also has to be your domain or a subdomain of it.

Confirm who answers DNS for your domain

A record saved in a console that your domain doesn’t delegate to is invisible to receivers, whatever that console reports.

A DKIM record only takes effect if Cloudflare is answering DNS for the domain, and that depends on the nameservers set at the registrar pointing to the Cloudflare nameservers shown in the dashboard. Open the domain in Cloudflare and check the Overview page, which confirms whether Cloudflare is active. If the nameservers point to another provider, the record has to be added there instead, because it will not take effect at Cloudflare.

Add the record in Cloudflare

Copy both pieces from the platform’s DKIM or email authentication page and keep that tab open until the check at the end passes. Laid out the way Cloudflare expects it, the record looks like this:

google._domainkey
v=DKIM1; k=rsa; p=<the long public key string the mail provider issued>

Type takes TXT for most DKIM keys, or CNAME when the mail provider specifies it, such as Microsoft 365. The Name field takes the selector part alone, for example google._domainkey or selector1._domainkey, because Cloudflare appends the domain automatically, so typing the full host such as selector1._domainkey.yourdomain.com produces a doubled, broken host. The Content field takes the key value pasted exactly as the provider gave it, or the target host for a CNAME entry. TTL stays on Auto unless you have a reason to set it yourself.

1. Sign in to Cloudflare and select the domain from the account’s domain list.
2. In the left-hand menu, open the DNS section, labelled DNS / Records.
3. Click Add record to start a new entry.
4. Set Type to TXT for most DKIM keys, or to CNAME only when the mail provider specifically says so.
5. In the Name field, enter only the selector part, such as google._domainkey or selector1._domainkey, and leave the domain off the end.
6. In the Content field, paste the long key value exactly as the mail provider gave it, or the target host for a CNAME record.
7. Leave TTL set to Auto.
8. Click Save to publish the record.
9. For a CNAME record, set the proxy status toggle to the grey cloud, DNS only, rather than the orange proxied cloud.

Before you save, compare the last few characters of the pasted value with the platform’s page, because a copy that stops early publishes a key that will never verify, and the console won’t warn you. Check the selector in the name against the platform’s page in the same pass.

A few traps are specific to Cloudflare:

• Putting the full domain in the Name field creates a broken host with the domain twice, because Cloudflare already appends it to whatever is typed there.
• DKIM public keys run to hundreds of characters, so nothing may be cut off and no stray spaces or line breaks may creep in during copy and paste. Cloudflare splits a long TXT value into segments behind the scenes, and that behaviour is correct.
• Adding quote marks by hand corrupts the record. Cloudflare handles the quoting on its own, so only the plain value should be pasted.
• A CNAME record left on the orange proxied cloud resolves to Cloudflare’s own proxy rather than the mail provider’s value, so it must be set to the grey cloud, DNS only.
• The selector typed in the Name field must match what the provider expects character for character, because that exact match is how a receiver finds the right key.
• Type has to follow whatever the provider specifies. If the provider says CNAME, the record is entered as CNAME with the target host as the content, not converted to TXT.

Save, then wait, then check

DNS changes at Cloudflare take minutes to a couple of hours before DKIM starts validating, and the saved record appears listed on the domain’s DNS / Records page alongside the domain’s other entries.

Once the record shows in the console, run the free scan against your domain. It asks DNS for the selector the way a receiving server does and tells you in plain words whether the key is published and readable.

A second check closes the loop. Send a message from the domain to a mailbox you control and open the Authentication-Results header. dkim=pass with your domain in header.d= means the signature verified against the key you published. dkim=fail or dkim=none with the record in place points at the selector or at the platform side, and the next section says where to look.

When the key is missing or malformed

Without a record at the selector, the receiver gets no key and the message carries no verified signature. It won’t bounce on that alone, though DMARC then has only SPF to lean on, and SPF breaks on forwarding, so the quote a customer forwards to a colleague arrives with neither.

A malformed record fails in the same quiet way: a p= value cut short, a stray space or line break in the middle, a doubled host such as mail._domainkey.yourdomain.com.yourdomain.com, or a selector that’s off by one character, and the receiver logs dkim=fail or dkim=permerror and moves on. You hear nothing unless DMARC reports are arriving, and the DMARC piece shows how those reports expose a DKIM failure per sending source.

The census shows how ordinary that silence is. Of the 75,823,110 domains where the September 2026 census could run the DKIM check, it found a key at a known selector on 37,999,462 (50.1%). That check works the way any checker does: there’s no way to list the DKIM records on a domain, so it can only ask for selectors it knows to try, and a platform with an unusual selector can read as absent when the key is fine.

If your scan reports nothing found while the record sits in the console, finding your DKIM selector shows how to read the live selector out of a sent message’s headers before you change anything.

Work a failure in order: the selector spelling first, the nameservers second, then the tail of the pasted value, then whether the platform still needs you to switch signing on.

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.