Etiquette, a French word whose literal meaning in English is ticket, today denotes the conventionally accepted rules, or customary norms that govern proper social and professional behavior. It means having good manners, in other words. Practicing proper etiquette then, is an individual's ticket to being accepted within a desired social or professional circle.
Cyberspace is a World Wide Web of Internet connected computers playing host to a multitude of social and professional circles whose members use it for communicating and sharing information. Within its confines, there is an emerging code of conduct to which online users are expected to adhere. In the pop-culture of the computer world it is called netiquette.
The recognized conventions of proper netiquette have evolved more out of commonsense than anything else and are certainly not hard and fast rules with formal penalties for disregarding them. Consistent breaches, however, quite often result in the offender being subjected to negative peer pressure, disapproval, and eventual disdain from the more scrupulous netiquette practitioners within a given circle of Internet users.
When writing business email it's wise to remember, the old saying "the pen is mightier than the sword." It's a saying that cuts both ways. Words can be enormously destructive as well as extraordinarily constructive and so it's up to the wordsmith, which way they cut. Naturally then, words should be selected with care. Here's a general rule: be nice, be thoughtful, be mindful of your words, and above all, say unto others, as you would have them say unto you. It's the Code of the Net.