Yes you can do all that, not too difficult.
The easiest way to manage the users is with a database, most people use mySql. There are instructions in the Tomcat docs for setting up a database. If you get mySql, also get a GUI to help you manage it, working with databases from the command line is not much fun.
As for the E-Mail, look for tha javaMail API.
On the Sun site there are dedicated forums for mail, google for sun java forum and you should find them.
If you search the sun forums you will find most of the code you require.