With so many messages, it's easy to get overwhelmed by the sheer volume. Using an appropriate subject line helps people find your message easier. Similarly, if you reply to a message and end up changing the subject, insert a different subject line. Be careful with acronyms and abbreviations. We're a pretty diverse group and might not understand your special shortcut.
New readers are often at a loss as to our unique jargon.
On this same note, remember that we're a multinational group. Use smiley faces to show intent. Email doesn't show mood or attitude. You have to let folks know if you are being humorous or joking with someone. If you don't like someone's comments tell him or her personally, one on one, off the list.