Email continues to create problems for me and some of my colleagues. Here are a few things to consider and be diligent about.
Be circumspect about what you write. Assume any email you write may be forwarded, either intentionally or by mistake, to the "wrong" party.
Wait 24 hours. Don't hit the reply (or forward) key in a rush. This may lead to saying things you regret later.
Turn it off. Limit how many times a day you look at it. It can waste a lot of time and be a significant distraction. Do you really need email on your mobile phone?
Think about the informality of your style. Perhaps the formality of what you write should be in proportion to the seniority of (or your personal closeness to) the person you write to.
The amount of time you spent composing an email should be in proportion to its importance.
Don't use the reply option if the subject of your email is different to the message you are replying to. This is a lazy way to find someone's address, but just confuses or irritates the recipient.
Three years ago I wrote a similar post.
I welcome comments and war stories.