Business E-mail: Guidance for Users

Advantages:
Enables fast communication, providing efficient transmission and interaction as well as more efficient preparation than other methods of writing.
Reaches many people simultaneously, in multiple locations around the globe and in different time zones; permits portability of communication with access anywhere the internet is available.
Distributes documents efficiently, especially compared with express mail or courier.

Disadvantages:
Fails to assure immediate response or even that audience reads the message
Requires accommodation for technology of some audiences because different email systems don’t support the same devices
Lacks privacy because messages may be printed, distributed, forwarded, or saved by the recipient for later dissemination. In some countries, emails may be illegally monitored and even subpoenaed in a lawsuit
Omits face to face non verbal cues that help speakers convey that they mean and help listeners interpret the message.
Risk miscommunication because writers may prepare emails too quickly and/or respond without adequate reflection; or readers may only glance over the message.
Records the conversation and leaves a paper trail, which can come back to haunt the writer

2.-
Select the complete distribution list before you write.
Compose a fully functional subject line
Apply the “top of the screen” test
Write in short chunks
Design for “high skim value”

3.-
Vary your style
Compensate for lack of nonverbal cues
Use jokes and informal idioms with great caution

4. - I think that knowing the structure of the email is very important to deliver a better message to the audience.
Also the disadvantages are important because that gives an idea of when is better not to use emails