When you use JavaMail to send an e-mail, and you don't get any exceptions but the e-mail doesn't arrive, the next step is to ask the administrator of the SMTP server to investigate.
In this case, that administrator is you. You will have to see what logging James does. It's quite possible you have configured it incorrectly. It might not have a connection to the Internet, or you might have set it up in such a way that other servers won't talk to it. Anything is possible. I recall that it comes with how-to documentation but it's a few years since I looked at it.
If you don't want to become an administrator, perhaps
you should find another server you can use. Then you can ask its administrator to deal with this sort of problem.