DKIM, or DomainKeys Identified Mail, 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 using a private key held by the sender's mail server. When the email is received, the recipient's server can check this signature against a public key published in the sender's DNS records. This process ensures that the email has not been altered in transit and confirms that it genuinely comes from the claimed sender's domain. By implementing DKIM, organizations can reduce the risk of email spoofing and improve their overall email security.