The concept "think before you speak" didn't apply to written communication, but email has made poor etiquette as easy as clicking Send. Just because it's fast and free doesn't mean you should be sloppy and thoughtless. Here are some things to keep in mind.
Email is not private. Logistically, email is like a postcard traveling through the Internet, and once it reaches its destination, it can be easily forwarded and copied, accidentally or on purpose. Plus, if you're using company email, your boss has the legal right to monitor your correspondence.
Watch what you write. Without body language, tone of voice, or even handwriting, your words can come across differently than you intend. Save bad news for the phone. And don't write and email when you're angry; it only takes a few seconds to say something you'll really regret.
Read what you write. Check your spelling and grammar.
Be mindful of who's in the To: line. Don't forward anything that the sender would want to keep private. Watch those group emails. If you don't want anyone to know who else is receiving the message, or if some recipients want to keep their addresses private, use the BCC field.
Don't write in all capital letters, unless you want recipients to think you're shouting.
Put thought into attachments. They can take a long time to send and receive. Before you send someone a file, make sure they want to receive it and that they have software to read it.
To save typing time and to add emotion to what some people think is a bland way of corresponding, some people use abbreviations and symbols in email correspondence. Here are a few that you might come across. Usage of these shorthand designations really is disappearing as people's typing skills improve and they learn that such abbreviations are examples of extremely poor writing ability. We present them here because others may use them and you need to understand them when they are employed.
Well BBFN, this is the EOL, but IMHO these are, FYI, confusing :-( , BYKT, but OTOH maybe you are <s>,