RFC 3207 (rfc3207) - Page 2 of 9
SMTP Service Extension for Secure SMTP over Transport Layer Security
Alternative Format: Original Text Document
RFC 3207 SMTP Service Extension - Secure SMTP over TLS February 2002 TLS [TLS], more commonly known as SSL, is a popular mechanism for enhancing TCP communications with privacy and authentication. TLS is in wide use with the HTTP protocol, and is also being used for adding security to many other common protocols that run over TCP. This document obsoletes RFC 2487. 1.1 Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC 2119]. 2. STARTTLS Extension The STARTTLS extension to SMTP is laid out as follows: (1) the name of the SMTP service defined here is STARTTLS; (2) the EHLO keyword value associated with the extension is STARTTLS; (3) the STARTTLS keyword has no parameters; (4) a new SMTP verb, "STARTTLS", is defined; (5) no additional parameters are added to any SMTP command. 3. The STARTTLS Keyword The STARTTLS keyword is used to tell the SMTP client that the SMTP server is currently able to negotiate the use of TLS. It takes no parameters. 4. The STARTTLS Command The format for the STARTTLS command is: STARTTLS with no parameters. After the client gives the STARTTLS command, the server responds with one of the following reply codes: 220 Ready to start TLS 501 Syntax error (no parameters allowed) 454 TLS not available due to temporary reason Hoffman Standards Track
