Email Authentication: SPF, DKIM and DMARC in Plain Language
Published August 12, 2026
A plain-language introduction to the three common email authentication technologies businesses encounter.
A plain-language introduction to the three common email authentication technologies businesses encounter.
Email Authentication: SPF, DKIM and DMARC in Plain Language
Email systems use several mechanisms to help receiving servers determine whether a message is legitimate.
SPF identifies permitted senders
SPF provides information about which systems are authorized to send mail for a domain.
DKIM adds a signature
DKIM allows a sending system to attach a cryptographic signature that can be checked by the receiving side.
DMARC adds policy and reporting
DMARC builds on SPF and DKIM and allows a domain owner to describe how authentication results should be handled.
Why this matters to a business
Businesses often use several services that send email: Microsoft 365, websites, marketing platforms, accounting systems and other applications. Adding a service can require changes to the domain's email configuration.
Change email settings carefully
Email authentication records are part of the infrastructure. A small mistake can affect legitimate mail, so changes should be planned and tested rather than copied from a generic example without understanding the existing setup.