There seems to be a prob with automated e-mails, i.e. they aren't sent out from the SMTP server on SF, at least that's what a user reported when he tried to change his e-mail addy and never got the e-mail and so his account became disabled (had to manually enable it from the admin panel). If it's not just with his mail addy but really because of the SMTP, no user can sign up to the boards. If SF doesn't offer an outgoing SMTP server, we'll either have to switch to another authentification method, e.g. admin enable, or use an account on an external mailserver.