Email--Uh-Oh! Take special care with those difficult folks who happen to be members of your family.
Tack this sentence to your computer. "If you're feeling angry, misunderstood, or otherwise intense, do not write that email!"
If you're the one on the receiving end of an emotionally loaded email, don't respond in kind. Instead, send a short email that says. "Thanks for your honesty. I'll give what you're saying lots of thought. Let's set up a time to talk on the phone, or when we're next together.
Take the exchange off email, and keep it off email.
Most disastrous are long emails, with all the details you believe will help the other person to see the irrefutable truth of your point, or really get the extent of your hurt. I haven't done the empirical research, but my informal observations suggest that the greater the word count, the faster the relationship slides downhill.
The tone (easily misread) and process of email is very different from a face-to-face conversation. Even a short constructive criticism on email can lead to escalating intensity. A therapy client of mine, Gennie, was irritating at her younger brother, Joe, who often crashed at her house without lifting a finger to help out.