SMTP mail order definition of the transmission or by user-defined functions. It is an order from <CRLF> end of the string. With the parameters of the case, ordered by <SP> itself and separate parameters, If the parameter can not bring direct and <CRLF> link. One format must receive site and the format. Discussed below SMTP orders and responses. Send mail to the operation involves different data objects, which by different parameters interconnected. MAIL return path is the order parameter, which is the path forward RCPT order parameters, DATA date of the mail order parameters. These parameters or data object must follow in order. This model also requires a different buffer to store these objects, in other words, there is a path back buffer a forward path buffer zone, a buffer zone Mail. Specific order to generate their own buffer zone, or one or more of the buffer contents were removed.

    HELLO (HELO)

    order for this to the receiving SMTP SMTP confirm this. Send domain parameters including SMTP host name. By the receiving SMTP authentication order to connect to this SMTP confirmed receiving SMTP. OK primer in response to orders and send and receive confirmation SMTP entered the initial state, that is to say, no operation is being executed. All state table and buffer zones have been cleared of quilts.

    MAIL (MAIL)

    This Order will be used for start-mail sent to more than one mailbox. Parameters include restoring domain path. Return to the path including the optional mainframe and mail senders list. When the host list, it is a source of return path, It shows that this mail is from the host table on January 1 this transfer (a mainframe is the last one is now receiving mail server ) overnight. This table can also be made to send non-return of the source of signal transmission path. Every transfer mainframe addresses were added to the beginning of this table, it must use this instead of receiving IPCE.

    SMTP命令定义了邮件传输或由用户定义的系统功能。它的命令是由<CRLF>结束的字符串。而在带有参数的情况下，命令本身由<SP>和参数分开，如果未带参数可以直接和<CRLF>连接。邮箱的语法格式必须和接收站点的格式一致。下面讨论SMTP命令和应答。发送邮件操作涉及到不同的数据对象，它们由不同的参数相互连接。回复路径就是MAIL命令的参数，而转发路径则是RCPT命令的参数，邮件日期是DATA命令的参数。这些参数或者数据对象必须跟在命令后。这种模式也就要求有不同的缓冲区来存储这些对象，也就是说，有一个回复路径缓冲区，一个转发路径缓冲区，一个邮件内容缓冲区。特定的命令产生自己的缓冲区，或使一个或多个缓冲的内容被清除。

    HELLO (HELO)

    此命令用于向接收SMTP确认发送SMTP。参数域包括发送SMTP的主机名。接收SMTP通过连接确认命令来向发送SMTP确认接收SMTP。引命令和OK响应确认发送和接收SMTP进入了初始状态，也就是说，没有操作正在执行，所有状态表和缓冲区已经被子清除。

    MAIL (MAIL)

    此命令用于开始将邮件发送到一个多个邮箱中。参数域包括回复路径。返回路径中包括了可选的主机和发送者邮箱列表。当有主机列表时，它是一个回复路径源，它说明此邮箱是由在表中的主机一一传递发送（第一个主机是最后一个接收到此邮件的主机）过来的。此表也有作向发送者返回非传递信号的源路径。因为每个传递主机地址都被加在此表起始处，它就必须使用发送IPCE而不是接收IPCE.