There are a number of scenarios in which senders may be required or compelled to send a bulk message despite the fact that such messages are highly likely to exhibit poor delivery metrics such as increased bounces or complaints. These messages are not intended to be used for standard marketing or transactional notices; these are the exceptions to the rule. Prominent examples of high-risk sends would be items such as breach notifications, product recalls, health and safety notices, or other notifications that might need to be sent to individuals who have been previously been suppressed or unsubscribed.

This document recommends a set of best practices for authenticating email messages using the security protocols Sender Policy Framework (SPF), Domain Keys Identified Mail (DKIM), Domain-based Message Authentication, Reporting & Conformance) DMARC and Authenticated Received Chain (ARC). (Another security protocol, SMTP authentication, meaning the presentation of credentials during the submission of a message by a Mail User Agent (MUA) or Mail Submission Agent (MSA) to a Mail Transfer Agent (MTA) serves a different purpose and is outside the scope of this document.)