She was my first love and I hers. We were together from about the age of 17 for about five years and not a day has gone by where I didn't think of her. Because of familial issues and her wanting to continue on with medical school, things ended. It was actually a lot more than that. I would've easily waited for her to finish her schooling if it weren't for my mother's ill health. I decided to find someone from the old country with "traditional" values that would be able to care for my mother. She ended passing away less than a year after I got married.
Fast forward 15 years... I am still married with 3 children. My ex lives in another state. I don't know if she's married or not. I'm not looking to change either of our situations but the thing is, she was a great friend and I would like to rekindle only that part of our relationship where we can chat via email once in a while.
That being said, what would be a safe way to initiate this through a first email?

Ask your wife first, that's the best way and if you do anything, good intentions or not before talking to the woman you are married to, you are an idiot!

^ I concur with Tal.

Far too risky without mentioning it to your wife. It'd only take a 'bad day' for it to go out of control.

Old friends or not.. what happened in the past should stay there. It's far to easy to get caught up in what if's and what could have been's.

I would say that you are perhaps considering more than just a friendship and by now they are a doctor, most likely married, maybe kids and her husband may not be really great about your wanting to be friends again either.

But there is face book, some of the school reunion web sites, and she is a doctor, so searching the medical license web sites for various states could find her also.