GreenMail 介绍
GreenMail 是一组主要用来做测试用的邮件服务器，支持 SMTP、POP3、IMAP 等，可以用来嵌入到任何的 Java 程序中。
示例代码
public void testYourSendingCode() throws Exception {
GreenMail greenMail = new GreenMail(); //uses test ports by default
greenMail.start();
GreenMailUtil.sendTextEmailTest("to@localhost.com", "from@localhost.com", "subject", "body"); //replace this with your send code
assertEquals("body", GreenMailUtil.getBody(greenMail.getReceivedMessages()[0]));
greenMail.stop();
// **That's it!**
}