DKIM record checker

Finds the DKIM key at <selector>._domainkey on your domain and reads its length and flags. Enter your selector if you know it; otherwise it tries the selectors the common providers use.

Why you have to know the selector

A DKIM key is published at <selector>._domainkey.<yourdomain>, and the selector is a name your mail provider picked: google, selector1, k1, s1 or a random string. DNS cannot list them, so no tool can answer "does this domain have DKIM" from the domain alone. This one tries 22 common selectors and says so when it finds nothing. To get yours exactly, open any email you sent, view its raw headers and read the s= value in the DKIM-Signature header.

What Gmail and Yahoo ask for

Gmail's sender guidelines (read 2026-10-30) require SPF or DKIM from every sender to Gmail, and both SPF and DKIM plus DMARC from anyone sending more than 5,000 messages a day. Sending to personal Gmail accounts needs a DKIM key of 1024 bits or longer, and Google recommends 2048. Yahoo's Sender Hub asks for SPF and DKIM from bulk senders and a key of at least 1024 bits.

Flags that make a key do nothing

An empty p= means the key was revoked, so mail signed with it fails. t=y marks the domain as testing DKIM, which tells receivers not to treat a failure any differently from an unsigned message (RFC 6376). Both are common leftovers from a setup that was never finished, and both are shown here.

Other checks

  • SPF record checkerReads the live SPF record, resolves every include it points at, and counts the DNS lookups. Over ten, receivers stop evaluating your SPF entirely.
  • DMARC record checkerReads the record at _dmarc on your domain and explains the policy it publishes — including the cases where a record exists but does nothing.
  • MX lookupResolves the MX records and names the provider behind them — which decides whether an address on this domain can be checked before you send to it.
  • Cold email checkerPaste the subject and the body. Each finding says whether it comes from a published rule, with the source and the date we read it, or is only our judgement. Nothing is sent anywhere, and there is no score.
  • Cold email deliverability auditEvery DNS check on this site at once, for a domain you are about to send from. It takes about a second and touches nothing but DNS.

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