JMail 异常: java.lang.NoClassDefFoundError: javax/activation/DataSource

异常提示: 

Exception in thread "Thread-1" java.lang.NoClassDefFoundError: javax/activation/DataSource
         at com.roadway.edserver.blo.SenderBO.<init>(SenderBO.java:24)
         at com.roadway.edserver.blo.SenderManager.managerSendingMail(SenderManager.java:37)
         at com.roadway.edserver.blo.SenderManager.run(SenderManager.java:17)
         at java.lang.Thread.run(Thread.java:595)
   原因是项目中没有加入activation.jar包.