You can e-mail Dwight directly.
But please note that he gets tons off e-mail and though he tries to read all of it he can't answer every one of them. Though he tries his very best and take into account that it's very rare that you will get an reply within the first couple of days of sending an e-mail it will more likelly be several weeks.
If you want to obtain his autograph please don't send him a request for it there are currently only two ways of obtaining one either visit a convention Dwight attends and has a autograph signing session at or enter a contest on his official fansite ones one is open and you'll have a chance of winning one there.
His email address is:
Don't forget that this email is routed directly to him. Please be polite.