Can your server send mail from other applications, like WordPress? What hosting environment are you using?
My guess is that your box doesn’t support PHP mail. I had the same problem, but I integrated users with my WordPress install so I got in with my admin account.
There is an SMTP plugin floating around but I haven’t gotten it to work, and it doesn’t support SSL. For now I’ve simply replaced the register link on bbpress with the link to my WP register page. (WP has a host of smtp plugins that work great).
That’s probably more than you needed to know but maybe I was able to preempt a few issues you might run into.
Just to follow up, I found/installed the Cimy SMTP for bbpress plugin which both works around disabled phpmail and supports SSL, and it works!
Check the links in this post regarding Cimy SMTP for bbpress.
https://bbpress.org/forums/topic/user-registration-password-mails-not-sending#post-55702