DKIM (DomainKeys Identified Mail)
A cryptographic signature added to outgoing emails that proves the message really came from your domain and was not tampered with.
DKIM adds a digital signature to the header of every email you send. The receiving mail server uses a public key published in your DNS to verify the signature. If it matches, the receiver knows the email genuinely came from your domain. Setting up DKIM is one of the three pillars of email authentication (alongside SPF and DMARC) and is required by Gmail and Yahoo for any sender mailing more than 5,000 messages per day.
Related terms
SPF (Sender Policy Framework)
A DNS record that lists which servers are allowed to send email on behalf of your domain.
DMARC
A policy you publish in DNS that tells inbox providers what to do if SPF or DKIM checks fail.
Deliverability
The ability to consistently land in the inbox rather than the spam folder or being rejected.