DMARC is a way to make it easier for email senders and receivers to determine whether or not a given message is legitimately from the sender, and what to do if it isn’t. This makes it easier to identify spam and phishing messages and keep them out of peoples’ inboxes.
DMARC is a proposed standard that allows email senders and receivers to cooperate in sharing information about the email they send to each other. This information helps senders improve the mail authentication infrastructure so that all their mail can be authenticated. It also gives the legitimate owner of an Internet domain a way to request that illegitimate messages – spoofed spam, phishing – be put directly in the spam folder or rejected outright.