Missing activation DataHandler class

Answer 1

My guess is you're using JavaMail to send an email, but you don't need attachments.

The activation framework is used to find handlers for more advanced situations - such as sending attachments. JavaMail will look for the JAF when it's first initialized. If your program is working without it, you don't need to worry about the warning.

(Our build system always had this and it never caused a problem.)