I never check my e-mail. If someone wants to contact me, PMs are the only way. I know several people like me that do the same thing as well. It's up to you, but I'd have some sort of PM / in site message system.
By the way, IceBB is even better than PHPbb3 (in my oppinion), and it's under a GNU licnense like PHPbb / SMW / etc. It would likely not be worth the trouble of switching and getting used to the new software though.