What are email etiquette?

Email etiquette refers to the principles of behavior that one should use when writing or answering email messages. It is also known as the code of conduct for email communication. It depends upon to whom we are writing- Friends & Relatives, Partners, Customers, Superior or Subordinates. 
Some rules for Email etiquette are:

• Don’t be sloppy in an attempt to be friendly.
• Watch your grammar, spelling, and punctuation.
• Avoid talking aimlessly in emails.
• Choose your subject wisely.
• Keep your emails organised.
• Reply to emails promptly.
• Delivery requests and sending receipts.
• Send smaller files, compress them.