DKIM

DKIM (DomainKeys Identified Mail) is an email security standard that lets the receiving mail server verify that an email was actually sent by the domain it claims to be from and was not modified in transit. It works by adding a cryptographic signature to every outgoing email, which the recipient can verify using a public key published in your DNS records. DKIM is one of three email authentication standards (along with SPF and DMARC) that help prevent email spoofing and improve deliverability.