rfc821 笔记

                      +----------+                                     +----------+
   +------+       |                |                                    |               |
   | User |<-->|                |      SMTP                      |               |
   +------+       |  Sender- |     Commands/Replies  | Receiver-|
   +------+       |   SMTP    |    <-------------->           |     SMTP  |                 +------+
   | File   |<-->|               |    and Mail                    |                |         <-->| File       |
   |System|     |               |                                     |                |                | System|
   +------+       +----------+                                     +----------+                  +------+
                       Sender-SMTP                Receiver-SMTP

 

                                       Model for SMTP Use

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连接和断开:

1. s:HELO <SP> <domain> <CRLF>
    r:250
 2.s:QUIT <CRLF>
    r:221

 邮件发送步骤:

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

//可以重复多次
3.s:DATA <CRLF>

   r:354 //ok 

   s: 信件内容,包括 Date, Subject, To, Cc, From 等. <CRLF>.<CRLF>表示结束

   r:250//ok