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An encyclopedia of email marketing, written for the people who do it. One page for every protocol, platform, email type, metric and law, each sourced, kept current, and backed by what brands actually send.
Deliverability and authentication
Whether email reaches the inbox: the DNS records that prove who sent a message, the rules mailbox providers enforce, and the reputation that decides the rest.
DMARC
Email authentication protocol
The DNS policy that ties SPF and DKIM to the From address a reader sees, tells receivers what to do with mail that fails, and asks them to report back. Now RFC 9989.
New entries are added every week. Our own figures come from the emails brands send to subscriptions of ours; Research explains how.