Whether your emails are for your family, friends, work or business, it is always possible to improve your writing and make your emails more interesting to read and of a better quality.  Emails are often written very quickly and time isn’t taken to reflect on what you are trying to say or how you are saying it.  Certainly, you can get away with not having perfect grammar or spelling, but if you take the time and trouble to make your emails free from errors, then they are much easier to read: so ensure that you pass them through an online grammar and spell checker.

Don’t attempt to make your emails too witty or funny. If you want to tell a funny story, just tell it and hopefully the humour will just stand out: otherwise if you try too hard to be funny, you can end up killing off the humor.

Don’t use capitals because these are hard to read. Using capitals makes you seem poorly educated and it looks like you are ‘shouting’.  Stick to an appropriate blend of upper and lower case.

Do ask after the other person.  Everyone gets emails where people just go on about their day or their holiday, their work or how beastly their friends or colleagues are.  The emails that say all this, but also take the time to say ‘How are you?  How are you feeling today’ or similar, are the ones that simply stand out and make the reader more inclined to respond.

Finally, don’t be offensive in emails.  There is no need and since the other person cannot see whether or not you are joking or just having a laugh, it is really easy to cause serious offence.  So reserve the risqué jokes for when you are face to face.

(from http://www.grammartips.net)