http://www.integramod.com + http://www.mail2forum.com/

As my contact told me it's a bit of a beast to setup, but with those 2 mods you could completely ditch yahoo and still allow people to do it from e-mail, including replies through e-mail (not sure if yahoo lets you do that or not) IE you reply to a message in the e-mail and it gets posted to the board as well as to the e-mail thread

And sure as hell don't ask me how this stuff works, I know just enough to make myself very dangerous to most servers :twisted: