Forum software with integrated webmail?

Is anyone aware of a forum software that allows you to also enter SMTP data into a user account and therefore check your email through the forum? Basically, a forum software that has integrated webmail. Does anyone know of anything like this - hell, do any of the main players like phpBB or Invision Board do this sort of thing?

Isn’t there an old saying that any product is not really feature complete until they add an email client? I bet someone has one somewhere.

How old could that saying be, really?