Terminology Index

Glossary

2953 terms

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32

SMTP

Simple Mail Transfer Protocol: the protocol that moves email between servers across the internet. Foundational to email infrastructure and a target for both abuse and detection.

SMTP is the standard for sending email between servers, with clients submitting messages and servers relaying them. As foundational networking, it underpins both legitimate email and attacker activity, phishing, BEC, and credential abuse all ride SMTP. Defenders monitor SMTP traffic and metadata, enforce authentication (SPF, DKIM, DMARC) to limit spoofing, and recognize SMTP-related signals during investigation. Understanding the protocol is essential for email security and for reading mail-related logs and headers.

Introduced in: Networking Foundations

Examples

  • A mail server relaying messages to another via SMTP.
  • Recognizing SMTP traffic in network logs during investigation.
  • Pairing SMTP with SPF, DKIM, and DMARC to limit spoofing.