The way I see it is this… At some point you shared your life together, that ought to be celebrated, you also cared for each other, that too ought to be celebrated, you split up for some pretty solid reasons too, that ought to be noted (otherwise you’d still be together) And now you find yourself in contact again..
Excellent.
Keep it at e-mail level, keep it healthy and not “oohhhh I soooo misss you” stuff, build friendship again and keep it that way.
Simple contact with Ex’s can be quite nice, I’m in contact (about once a month or so) with a previous incarnation of MrsBouy and all’s very well indeed. We chat about sailing, where she’s going, her new boat, her life at work.. in fact it’s pretty much how it used to be with us two.. She’s in a relationship now, no idea if he knows we chat and if he’s a decent bloke he’ll not pry but respect her decision to chat to me, if he’s not then i’d be sorry to loose a friend who i spent the best part of all my 30’s with, and that would be very sad.
I’d say keep the distance, that’s healthy.