I think there must be a huge market for a course "Dealing with email"
I once went on a course entitled "managing across cultures", which was primarily about working in a multi-national company, with different ways of doing things in different countries. It had a great piece on email barnies - which is applicable both to linguistic/cultural differences as well as just the usual awkwardness. The trick is this: when you read an email that gets your hackles up, stop a minute and write down - on paper, not on-screen - what the sender *actually* said. No inferences, no assumptions. Then simply note, for each entry, whether the statement is true, false, or unknown.
Pretty soon, most such angry exchanges can be narrowed down to a minor misunderstanding, since most of us are actually quite reasonable most of the time.