Hi martino,
You would have to set up some kind of script to do that. phpBB lets people sign up for email accounts if you configure it that way. I would check out
www.hotscripts.com to see if you have find something about it. I honestly don't know how you could do it other than through a script.
As for staff, this isn't official support but our membership forum. Anyone can answer questions for anyone else. We try to help each other out here just like you did for jaser by providing information on the webmail alternative url. I just thought I would point this out, since I try to respond to posts that I can, but there are a lot of posts each day and it is difficult to make a guarantee which ones I myself could answer. I really appreciate the assistance provided by all the members here, especially those who go out of their way to answer questions.
Have a Blessed Day