说明：  MessageDialog显示发送e-mail邮件的对话框。使用SMTP协议发送E-mail的步骤是这样的： （1）客户端连接某个E-mail服务器。 （2）客户端向该服务器发送一个E-mail。 （3） 客户端关闭到服务器的连接。 使用SMTP发送E-mail的工作非常简单，客户端软件建立到SMTP服务器的一个连接，接着向该服务器发送邮件，最后关闭连接。然后SMTP服务器获得邮件，并将其转发给相应的接收Email的邮件服务器。
(Showing MessageDialog Send e-mail message dialog box. Use SMTP protocol to send E-mail of the steps is as follows: (1) clients to connect to a E-mail server. (2) the client to the server send an E-mail. (3) Close the client connection to the server. Use SMTP to send E-mail the work of a very simple client software to the SMTP server to establish a connection, and then to the server to send mail, and finally close the connection. SMTP server and then e-mail and forward it to the corresponding mail server to receive Email.)