Question 1

What is a DKIM selector?

Accepted Answer

A DKIM selector is the DNS label used to find the public key for a signed message, usually at selector._domainkey.example.com.

Question 2

What qualifies as a DKIM record?

Accepted Answer

A DKIM record is normally a TXT record beginning with v=DKIM1 and containing tags such as k= and p=, or a CNAME pointing to a hostname that publishes that TXT record.

Question 3

Why can multiple DKIM records be a problem?

Accepted Answer

A DKIM selector should publish one clear TXT record or one CNAME target. Multiple TXT records, or TXT and CNAME together, can make validation fail or behave unpredictably.

Tag	What It Does
`v=DKIM1`	Marks the TXT record as a DKIM selector record.
`k=rsa`	Declares the key type. RSA is the most common DKIM key type.
`p=`	Contains the Base64-encoded public key used to validate DKIM signatures.
`t=s`	Strictly limits use of the selector to the exact domain rather than subdomains.
`t=y`	Testing mode. Indicates the selector may still be in test use.
`n=`	Optional notes field for administrators.
`h=`	Optional list of acceptable hash algorithms.
`s=`	Optional service type tag, commonly email.

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