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TCP/IP 电子邮件 
Email is one of the most important uses of TCP/IP.
电子邮件最重要的一点是它也是使用TCP/IP的。
You Don't
禁止
When you write an email, you don't use TCP/IP.
当你写电子邮件时，你不必使用TCP/IP
When you write an email, you use an email program like Lotus Notes, Microsoft Outlook or Netscape Communicator.
当你在写电子邮件时，你可能会使用诸如Lotus Notes、Microsoft Outlook 或者 Netscape Communicator的来书写电子邮件程序。
Your Email Program Does
你的Email程序应该会用到以下方式：
Your email program uses different TCP/IP protocols:
你的电子邮件程序使用着不同的TCP/IP协议：
- It sends your emails using SMTP
• 通过SMTP发送邮件 - It can download your emails from an email server using POP
• 通过POP从电子邮件服务器上下载你的邮件 - It can connect to an email server using IMAP
• 通过IMAP连接到邮件服务器
SMTP - Simple Mail Transfer Protocol
SMTP-简易邮件转换协议
The SMTP protocol is used for the transmission of e-mails. SMTP takes care of sending your email to another computer.
SMTP协议是用于电子邮件的转换的。SMTP负责将你的电子邮件发送到其他的计算机上。
Normally your email is sent to an email server (SMTP server), and then to another server or servers, and finally to its destination.
通常情况下，你的电子邮件会首先发送到电子邮件服务器上（SMTP 服务器），然后再发送到另外的一个或几个服务器上，最后到达目的地。
SMTP can only transmit pure text. It cannot transmit binary data like pictures, sounds or movies.
SMTP只能传输纯文本。它不能传输像图片、声音或电影这样的二进制位数据。
SMTP uses the MIME protocol to send binary data across TCP/IP networks. The MIME protocol converts binary data to pure text.
SMTP使用MIME协议越过TCP/IP网络来发送二进位数据。MIME 协议能把二进位数据转换成纯文本。
POP - Post Office Protocol
The POP protocol is used by email programs (like Microsoft Outlook) to retrieve emails from an email server.
POP协议通过使用电子邮件程序（如Microsoft Outlook）来获取电子邮件服务器中的电子邮件。
If your email program uses POP, all your emails are downloaded to your email program (also called email client), each time it connects to your email server.
如果你的电子邮件程序使用了POP，那么所有的邮件将下载到你的邮件程序中（也叫做邮件客户端。如：Microsoft Outlook），每次上网时它都会自动联到你的电子邮件服务器上。
IMAP - Internet Message Access Protocol
IMAP-互联网信息访问协议
The IMAP protocol is used by email programs (like Microsoft Outlook) just like the POP protocol.
IMAP协议是通过运用电子邮件程序（如Microsoft Outlook）来使用的，类似于POP协议的。
The main difference between the IMAP protocol and the POP protocol is that the IMAP protocol will not automatically download all your emails each time your email program connects to your email server.
IMAP与POP的主要差别是：每次，当你的邮件程序连接到邮件服务器上时，IMAP协议不会自动下载你所有的邮件。
The IMAP protocol allows you to see through your email messages at the email server before you download them. With IMAP you can choose to download your messages or just delete them. This way IMAP is perfect if you need to connect to your email server from different locations, but only want to download your messages when you are back in your office.
在你下载邮件时，IMAP协议允许你在邮件服务器上浏览邮件消息。通过IMAP你可以选择是下载还是删除它们。如果你需要从不同的地方连入你的邮件服务器，使用IMAP是相当不错的选择；当你回到办公室的时候，你就可以把它们下载下来了。
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