DMARC protects email from spoofing, phishing and spamming. The protocol helps make certain that the listed sender is who they are supposed to be, making email users more secure and protecting brands against abuse of their images.
DMARC builds on the commonly-deployed Sender Policy Framework (SPF) and DomainKeys Identified Mail (DKIM) protocols. DMARC adds linkage to the author’s domain name with the :From: header and standardized policies for recipient handling of authentication failures. Receivers-to-sender reporting is improved for anti-spam purposes.
A policy for DMARC allows a sender domain to specify if its email’s use of SPF and/or DKIM. Policies can be set for sending email to a spam folder or reject it if the authentication methods fail. If an email recipient gets an email that fails these authentications, they also have an option to report it back to the sending domain.
DMARC only protects against direct domain spoofing. Users can still be fooled by similar domains that trick them by appearing close enough, e.g. domainname.com vs domaimename.com. The protocol also fails to protect against situations where the sender is faked as the same name as the recipient. Despite limitations, DMARC’s additional protections were welcomed. Within a year of its debut in 2012, DMARC was deployed on 60 percent of email inboxes.