There are three primary authentication methods used in email marketing:
Sender Policy Framework (SPF): An email authentication method that allows domain owners to specify which mail servers are permitted to send email on behalf of their domain. DomainKeys Identified Mail (DKIM): A method that uses an encrypted signature to verify that the email message has not been altered during transit and is indeed from the specified domain. Domain-based Message Authentication, Reporting, and Conformance (DMARC): A policy layer that builds on SPF and DKIM, allowing domain owners to specify how unauthenticated emails should be handled.