From: Author: (08:08:00)
4.1.2. COMMAND syntax format
A command is composed of an authorization code and a subsequent parameter field. The command code is composed of four letters, no difference
Case. Because the following commands serve the same purpose:
MAIL Mail mail
This is also applicable TO the flag that directs any parameter value, such as to and. Command code and
Parameters are separated by one or more spaces. However, the parameters in the reply path and the forwarding path are case-insensitive.
. Especially on some hosts, "smith" and "Smith" are not a user at all.
The parameter field is composed of an indefinite string ending with <CRLF>. Before the receiver completely receives this sequence
No action will be taken. Square brackets represent optional parameter fields. If not selected, the system selects the default
.
The following is the SMTP command:
HELO <SP> <domain> <CRLF> MAIL <SP> FROM: <reverse-path> <CRLF>
RCPT <SP> TO: <forward-path> <CRLF>
DATA <CRLF>
RSET <CRLF>
SEND <SP> FROM: <reverse-path> <CRLF>
SOML <SP> FROM: <reverse-path> <CRLF>
SAML <SP> FROM: <reverse-path> <CRLF>
VRFY <SP> <string> <CRLF>
EXPN <SP> <string> <CRLF>
HELP [<SP> <string>] <CRLF>
NOOP <CRLF>
QUIT <CRLF>
TURN <CRLF>
The format of the above parameter fields is given below for the BNF format, where "..." represents
The domain is repeated once or multiple times.
<Reverse-path >::= <path>
<Forward-path >::= <path>
<Path>: = "<" [<a-d-l> ":"] <mailbox> ">"
<A-d-l >::= <at-domain >|< at-domain> "," <a-d-l>
<At-domain >::= "@" <domain>
<Domain >::= <element >|< element> "." <domain>
<Element >::= <name> | "#" <number> | "[" <dotnum> "]"
<Mailbox >::= <local-part> "@" <domain>
