Ask yourself: is e-mail the best form of communication in this situation? Making a telephone call or having a personal conversation is often more appropriate.
Stay away from emotion in an e-mail: anger, sarcasm and intimacy.
Know that an e-mail is in black and white and can be effortlessly forwarded intentionally or unintentionally.
Leave important e-mail for a moment. A day if possible. Read it again.
Eliminate spelling mistakes and inaccuracies.
A good e-mail is actually a letter, but not on paper.
After the salutation a comma and two blank lines.
The first sentence should preferably not start with 'I'. It's about the other person, the addressee, not you in the first place.
Do not use abbreviations. These are not always clear and they date from the time when there was little space. In an e-mail there is all the place in the world. Use that place sparingly but completely.
Enter the subject line to say what it is about. But also to attract attention and to stand out. 'Urgent' or 'Question' are not the best.
Use blank lines.
Use blank lines.
Do not use capital letters. IT SEEMS LIKE YOU ARE YELLING or angry or at the fair. Be thrifty with irony and jokes.
Don't write things you wouldn't put on a postcard.
Don't ask for a read receipt unless you really need to. It seldom is.
Add your sender information. A fixed signature containing all your contact information is useful in this regard.
Reply all e-mails within 24 hours. Or confirm receipt and report that you will reply later.
Don't use acronyms, W8ff, lol, OMG! Emoticons are also not recommended. Unless you're under 6 or want to scare people off for good. It is also completely unclear what most of those things want to say.
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