DKIM is used to verify the authenticity of messages sent from your domain.

DomainKeys Identified Mail (DKIM) is an email authentication method designed to detect email spoofing. It allows the receiver to check that an email claimed to come from a specific domain was indeed authorized by the owner of that domain.[1] It is intended to prevent forged sender addresses in emails, a technique often used in phishing and email spam.

Please head over to our automated DNS record guide to implement DKIM.

For a full explanation of DKIM, we recommend the Wikipedia article.