Email is not secure - don’t put anything in an email that you wouldn’t put on a postcard.
Don’t use UPPER CASE - it looks as though you’re shouting.
Use symbols to emphasize what you’re saying - eg that *is* what I meant.
Use underscores for underlining - eg _War and Peace_ is my favourite book.
Use smileys to show tone of voice - eg :-) ;-) :-( However, don’t assume that an insulting remark can be made more bearable by including a smiley.
Always include a subject heading with your message, and make sure it has something to do with the message you’re sending.
Wait overnight to send emotional responses to messages.
Never say something in an email that you would not be prepared to say to someone face-to-face.
Remember that the person receiving your message is a human being whose culture, language and humour may not be the same as yours. Remember that date formats, measurements and idioms (eg “that’s a red herring”) may not travel well. Be especially careful with sarcasm.
Keep your messages short and to the point. Remember that many people pay for connection to the Internet by the minute and the longer your message, the more they pay.
Don’t send attachments that are more than 1Mb in size - they take too long to download.