Glossary
Mail transport
SMTP
Simple Mail Transfer Protocol — the protocol servers use to hand messages to each other. It carries the message and the envelope around it, and authenticates nothing about the sender by itself.
Defined in RFC 5321.
Where this appears
The lessons that use this term, and what each is for.
Email Authentication FundamentalsThe path a message takesName every system a message passes through, and say which of them you control.Email Authentication FundamentalsInside an SMTP conversationRead an SMTP transcript and identify each identity the sending server claims.Advanced Email TrustWhat opportunistic TLS leaves openDescribe the downgrade an on-path attacker performs, and why the sender never notices.Advanced Email TrustReading oneName the cause behind each failure type a report can carry.