Is this guy a member of your religious community or does he know your rules? I have absolutely no problem with male friends and spending time alone with male visitors, even though I'm married, and in fact I would get really annoyed if someone only sent messages to me through my husband. That's just because I'm not of your faith (and I didn't know there was a faith where these rules still existed, other than places like Saudi Arabia. I guess I was really ignorant). I'm not saying you should hang out with this guy or answer the door if you don't feel comfortable, but maybe it's not the worst case scenario?