Enable DKIM at the mail provider, then publish the exact selector record it supplies in DNS.
Step by Step
- Open the email provider's domain-authentication settings.
- Generate or locate the DKIM DNS record.
- Copy the selector/host and value exactly.
- Add the requested TXT or CNAME record at the authoritative DNS provider.
- Return to the email provider and verify/activate DKIM.
If That Doesn't Work
- The selector is part of the DNS hostname and must be entered correctly.
- Do not alter long public-key values.