What is a DMARC record?
DMARC records are published in the DNS as text (TXT) resource records (RR) and announce what an email receiver should do with non-aligned mail it receives.
Consider an example DMARC record for the domain “sender.exampledomain.com” that reads:
In this example, the sender requests that the receiver outright reject all non-aligned messages and send a report, in a specified aggregate format, about the rejections to a specified address. If the sender was testing its configuration, it could replace “reject” with “quarantine” which would tell the receiver they shouldn’t necessarily reject the message, but consider quarantining it. DMARC records follow the extensible “tag-value” syntax for DNS-based key records defined in DKIM.