简单Mail传输协议。目标
![](https://www.godic.net/tmp/wordimg/5@@Xo7@GbnWkiw7IqTIJ794B35Qw=.png)
向用户提供高效、
![](https://www.godic.net/tmp/wordimg/vWbTKkO8M6bojv3ES@@SFdOKI39M=.png)
![](https://www.godic.net/tmp/wordimg/Wx6@m3e2JXZZ0SSksuq@@zBJZD4A=.png)
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
![](https://www.godic.net/tmp/wordimg/oq6eq7uYT9W79Qh6mshKuBTXH98=.png)
件传输。SMTP
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
![](https://www.godic.net/tmp/wordimg/TpXL4N9ryMhene8X24z@@hUhhyus=.png)
个重要特点
![](https://www.godic.net/tmp/wordimg/5@@Xo7@GbnWkiw7IqTIJ794B35Qw=.png)
它能够在传送中接力传送
![](https://www.godic.net/tmp/wordimg/oq6eq7uYT9W79Qh6mshKuBTXH98=.png)
件,即
![](https://www.godic.net/tmp/wordimg/oq6eq7uYT9W79Qh6mshKuBTXH98=.png)
件
![](https://www.godic.net/tmp/wordimg/vWbTKkO8M6bojv3ES@@SFdOKI39M=.png)
以通过不同网络上
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
主机接力式传送。工作在两种情况下:
![](https://www.godic.net/tmp/wordimg/TpXL4N9ryMhene8X24z@@hUhhyus=.png)
![](https://www.godic.net/tmp/wordimg/5@@Xo7@GbnWkiw7IqTIJ794B35Qw=.png)
![](https://www.godic.net/tmp/wordimg/@jXHPvcFZveaa1P3CxrV4j018qw=.png)
子
![](https://www.godic.net/tmp/wordimg/oq6eq7uYT9W79Qh6mshKuBTXH98=.png)
件从客户机传输到服务器;二
![](https://www.godic.net/tmp/wordimg/5@@Xo7@GbnWkiw7IqTIJ794B35Qw=.png)
从某
![](https://www.godic.net/tmp/wordimg/TpXL4N9ryMhene8X24z@@hUhhyus=.png)
个服务器传输到另
![](https://www.godic.net/tmp/wordimg/TpXL4N9ryMhene8X24z@@hUhhyus=.png)
个服务器。SMTP
![](https://www.godic.net/tmp/wordimg/5@@Xo7@GbnWkiw7IqTIJ794B35Qw=.png)
个请求/响应协议,它监听25号端口,用于接收用户
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
Mail请求,并与远端Mail服务器建立SMTP连接。
Smtp工作机制
SMTP通常有两种工作模式:发送SMTP和接收SMTP。具体工作方式为:发送SMTP在接到用户
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
![](https://www.godic.net/tmp/wordimg/oq6eq7uYT9W79Qh6mshKuBTXH98=.png)
件请求后,判断此
![](https://www.godic.net/tmp/wordimg/oq6eq7uYT9W79Qh6mshKuBTXH98=.png)
件
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