Sounds to me like this other man is enjoying the flirtation, and the little thrill from feeling wanted by you. But he doesn't really want it to go beyond that. That's probably why the contact stopped prior to him coming back into town. I'm betting when he's out of town again, he'll start right back up with the emails, etc. And when he does, you should cut it off completely. You're spending days crying and feeling miserable - this is bad for you, and you shouldn't participate in something that makes you feel bad.
And I agree with TealOrca12 that it might be wise to address your own marriage. Maybe he's just not the man for you. Or maybe you're seeking something you need from others, rather than give your husband a real chance to provide it. I don't know, but I think it's worth it to find out, for the well being of all involved, as well as for you.