Email & SMTP

STARTTLS

An SMTP extension that upgrades an existing plaintext connection to encrypted TLS, different from implicit TLS which starts encrypted from the beginning.

관련 프로토콜

SMTP

가이드에서 언급됨

Debugging SMTP Delivery Failures: 4xx Temporary vs 5xx Permanent Debugging & Troubleshooting

SMTP Authentication Methods Explained Email Delivery

RFC 5321: SMTP Protocol Deep Dive Protocol Deep Dives

RFC 959: FTP Protocol Deep Dive Protocol Deep Dives

관련 시나리오

Email Rejected Due to SPF/DKIM/DMARC Failures SMTP

550 Relay Access Denied — Cannot Send Through SMTP Server SMTP

535 Authentication Failed — App Password Required SMTP

503 Bad Sequence of Commands — AUTH Before STARTTLS SMTP

421 Service Unavailable — STARTTLS Required SMTP

정의 출처

RFC 3207 SMTP Service Extension for Secure SMTP over Transport Layer Security

RFC 4217 Securing FTP with TLS

관련 항목

TLS Handshake Security

SMTP Relay Email & SMTP

MTA (Mail Transfer Agent) Email & SMTP

SMTP Pipelining Email & SMTP

FTPS (FTP Secure) FTP & File Transfer

FTP over TLS (RFC 4217) FTP & File Transfer