Java Socket邮件发送程序SMTP客户端邮件发送程序的实现原理非常简单，首先建立和邮件服务器的Socket连接，然后和服务器握手，发送各个SMTP指令，并按照邮件格式封装邮件体内容，最后发送即可。-Java Socket client mail program SMTP mail program implementation principle is very simple, first create the Socket connection and mail server, and then shook hands and the server to send all SMTP commands and follow the message format encapsulates the content of the message body, and finally send it.