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.

関連プロトコル

SMTP

ガイドで言及されています

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

関連シナリオ

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

定義元

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

RFC 4217 Securing FTP with TLS

関連項目

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