Mail notification in a custom project (shell script) fails. It looks like activation.jar is not loaded:

Sending e-mails to: xxx@xxx.xxx
FATAL: javax/activation/DataContentHandler
java.lang.NoClassDefFoundError: javax/activation/DataContentHandler
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:620)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:260)
at java.net.URLClassLoader.access$100(URLClassLoader.java:56)
at java.net.URLClassLoader$1.run(URLClassLoader.java:195)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:620)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:260)
at java.net.URLClassLoader.access$100(URLClassLoader.java:56)
at java.net.URLClassLoader$1.run(URLClassLoader.java:195)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at java.lang.ClassLoader.loadClass(ClassLoader.java:299)
at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1346)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1205)
at javax.activation.MailcapCommandMap.getDataContentHandler(MailcapCommandMap.java:590)
at javax.activation.MailcapCommandMap.createDataContentHandler(MailcapCommandMap.java:
550)
at javax.activation.DataHandler.getDataContentHandler(DataHandler.java:611)
at javax.activation.DataHandler.writeTo(DataHandler.java:315)
at javax.mail.internet.MimeUtility.getEncoding(MimeUtility.java:248)
at javax.mail.internet.MimeBodyPart.updateHeaders(MimeBodyPart.java:1268)
at javax.mail.internet.MimeMessage.updateHeaders(MimeMessage.java:2012)
at javax.mail.internet.MimeMessage.saveChanges(MimeMessage.java:1980)
at javax.mail.Transport.send(Transport.java:97)
at hudson.tasks.MailSender.execute(MailSender.java:65)
at hudson.tasks.Mailer._perform(Mailer.java:73)
at hudson.tasks.Mailer.perform(Mailer.java:67)
at hudson.model.Build$RunnerImpl.post2(Build.java:138)
at hudson.model.AbstractBuild$AbstractRunner.post(AbstractBuild.java:243)
at hudson.model.Run.run(Run.java:595)
at hudson.model.Build.run(Build.java:103)
at hudson.model.ResourceController.execute(ResourceController.java:66)
at hudson.model.Executor.run(Executor.java:59)