SPF stands for Sender Policy Framework. It allows domain owners to specify which servers are authorized to send emails on behalf of their domain.
By implementing an SPF record, you can define a list of permitted sending servers in DNS. When receiving servers check the SPF record during the email authentication process, they can verify if the sending server is authorized to send emails on behalf of the domain. If messages are sent from servers outside the authorized list, it can be determined that the sender does not have the necessary rights, and the message is likely to be marked as spam.
Note: If you enable an SPF record, you can only use the email servers specified in the record for sending emails in the future.
DKIM stands for DomainKeys Identified Mail. It involves the server signing the outgoing email with a private key and the recipient's server verifying the signature using a public key. This allows the receiving server to determine if the sender is legitimate and if the message has been tampered with during transit.
By adding a DKIM record to the domain's DNS, the domain owner ensures that the outgoing emails are digitally signed. When the recipient's server receives the email, it can use the DKIM signature to verify the email's authenticity and integrity.
DMARC (Domain-based Message Authentication, Reporting, and Conformance) is a policy framework that enhances email authentication by leveraging SPF and DKIM. It allows the domain owner to specify what actions should be taken by the recipient's server if SPF and DKIM authentication fail for incoming emails.
DMARC enables better communication between sending and receiving servers and improves email authentication by utilizing existing SPF and DKIM records. It provides instructions to the recipient's server on how to handle emails that do not pass SPF and DKIM checks.
DMARC was developed to address the challenges faced by email senders in implementing comprehensive SPF and DKIM records. Many sending domains do not have SPF and DKIM records by default, making it difficult for receiving servers to establish a consistent policy. As a result, receiving servers often have to make their own decisions on whether to accept or reject unauthenticated emails. Therefore, the use of SPF and DKIM records alone does not guarantee email security.