There are several key methods of email authentication that you should be aware of:
SPF (Sender Policy Framework) SPF is a method used to prevent spammers from sending messages on behalf of your domain. It allows the receiving mail server to check if an email claiming to come from a specific domain is sent by an IP address authorized by that domain's administrators.
DKIM (DomainKeys Identified Mail) DKIM adds a digital signature to the headers of an email message. This signature can be validated by the receiving mail server to ensure that the email has not been altered and that it indeed comes from the claimed domain.
DMARC (Domain-based Message Authentication, Reporting & Conformance) DMARC builds on SPF and DKIM by adding a reporting function, allowing domain owners to receive feedback about messages that fail SPF or DKIM checks. It also provides instructions to the receiving server on how to handle failed messages.