Even during the times of Twitter and other social media websites email is still one of the biggest reasons people use the Internet for and no matter what the detractors say email is not going to be uncool for a long, long time.
When you are using email for personal purposes you can use it in whatever manner you feel like. I mean, your close friend, your sister, or your mother is not going to mind how long or short your message is and if you have proofread it or not, but if you use email as a business communications tool you need to know hoe to use your email effectively. Effective use of email not only makes your messages clear and concise, it also saves you lots of time.
For instance, don’t keep checking your email every 20 minutes, and don’t write emails that go on and on and on. You should use a clear subject so that the recipent knows why he or she is being sent that email, and use your proper name for the "From" field so that it doesn’t seem like spam.
Web Work Daily gives you some nice tips on how to use your email effectively.