Think twice before sending messages. E-mail can not be retrieved once sent. Never put private information into e-mail messages. They can be and often are read by other people. Make messages as short as possible.
Web communication is informal.
Do not correct or comment on typos or other mistakes. Do not expect immediate answers. Try to answer e-mail as quickly as possible. Writing in all capital letters is called shouting and is very rude. A flame is sending an angry message.