Ensure you have next jar files in your classpath:
activation.jar ((javax.activation.DataHandler)
You can download it from http://java.sun.com/products/javabeans/jaf/downloads/index.html.
mail.jar (for javax.mail.internet.MimeMultipart)
You can download it from http://java.sun.com/products/javamail/.
If you're using Axis (and I believe yes, because of this warning), put these two jar files in the same (i.e. WEB-INF/lib) directory where your axis.jar etc. resides.
Regards,
Milan Boruvka
http://www.boruvka.net/blog