+----------+ +----------+
+------+ | | | |
| User |<-->| | SMTP | |
+------+ | Sender- | Commands/Replies | Receiver-|
+------+ | SMTP | <--------------> | SMTP | +------+
| File |<-->| | and Mail | | <-->| File |
|System| | | | | | System|
+------+ +----------+ +----------+ +------+
Sender-SMTP Receiver-SMTP
Model for SMTP Use
連接和斷開:
1. s:HELO <SP> <domain> <CRLF>
r:250
2.s:QUIT <CRLF>
r:221
郵件發送步驟:
1. s:MAIL <SP> FROM:<reverse-path> <CRLF>
r:250//ok
2.s:RCPT <SP> TO:<forward-path> <CRLF>
r:250//ok 或者 550 //Failure
//可以重複多次
3.s:DATA <CRLF>
r:354 //ok
s: 信件內容,包括 Date, Subject, To, Cc, From 等. <CRLF>.<CRLF>表示結束
r:250//ok