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