Some business contacts will know you only through your email communication. The tone you convey in your online messages should be respectful, friendly, and approachable. In this article, I’m going to discuss email etiquette.

• Check mail promptly. Generally, a response to email is expected within 24 hours. Ignoring messages from co-workers can erode efforts to create an open, honest, and cooperative work environment. On the other hand, responding every second may indicate that you are paying more attention to your email than your job.
• Do not send messages when you are angry. Email containing sensitive, highly emotional messages may be easily misinterpreted because of the absence of nonverbal communication (facial expressions, voice tone, and body language). Sending a flame, the online term used to describe a heated, sarcastic, sometimes abusive message or posting, may prompt a receiver to send a retaliatory response.
• Use a professional email address. If you work for a company, you should use your company email address. But if you use a personal email account-whether you are self-employed or just like using it occasionally for work-related correspondences, you should pick an email address that presents as a professional.
• Be cautious with humour. Humour can easily get lost in translation without the right tone or body language. In a professional exchange, it’s better to leave humour out of emails unless you know the recipient well. Also, something that you think is funny might not be funny to someone else.
• Keep your fonts classic. For business correspondence, keep your fonts, colours, and sizes classic. Your emails should be easy for other people to read.
• Nothing is confidential. Always remember that all electronic communication may be stored and rebroadcast, so, don’t write anything you wouldn’t want everyone to see.
• Be certain individuals need a copy of the email, and forward an email from another person only with the original writer’s permission.
• Never address an email requesting general action to more than one person if you want to receive individual response. Sharing responsibility will lead to no one taking responsibility.
• Follow company policy for personal use of email, and obtain a private email account if you are job hunting or sending many private messages to friends and relatives.

Source: Carol, M. Lehman Business Communication, Cengage Learning