add mail.jar and activation.jar in ANT_HOME/lib or use both jar form your project/lib
问题描述：
ant执行发送email的功能时报错：java.lang.ClassNotFoundException: javax.mail.internet.MimeMessage
解决办法：
将mail.jar and activation.jar放到ant的lib下
转自：http://stackoverflow.com/questions/17302832/getting-error-message-java-lang-classnotfoundexception-javax-mail-internet-mim
原文：http://www.cnblogs.com/fatfatdachao/p/4054722.html