Failed to execute goal org.codehaus.mojo

[Masar92]

Exception in thread "main" java.lang.NoClassDefFoundError: groep3/Mail/Mail
at com.mycompany.cvo_crescendo_main.TestMail.main(TestMail.java:29)
Caused by: java.lang.ClassNotFoundException: groep3.Mail.Mail
at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)

this is the error , In the Class Mail , there is no fault , but it stil give a error!!
Can anyone help with this , ?