MTA stands for Mail Transfer Agent, I think, so apparently the app runs, but cannot use its email services.
I recommend that when running
Java via cron that you place the actual Java command in a script file and let cron run the script instead. It makes things a little simpler. You can run the script directly for debugging purposes (which is something I spent too much time doing just the other day!).
The secret of how to be miserable is to constantly expect things are going to happen the way that they are "supposed" to happen.
You can have faith, which carries the understanding that you may be disappointed. Then there's being a willfully-blind idiot, which virtually guarantees it.