DomainKeys Identified Mail (DKIM) is an email authentication method that helps verify the sender's identity. It uses a digital signature added to the email header, which is created by the sender's mail server. This signature allows the recipient's server to check if the email was indeed sent by the claimed domain and if it hasn't been altered during transit. When a recipient receives an email, their server can use the public key published in the sender's Domain Name System (DNS) records to validate the signature. If the signature matches, it confirms the email's authenticity, reducing the chances of email spoofing and improving overall email security.