We receive and send emails a lot nowadays.
I recently read an interesting article from which I extracted following good recommendations if you don't want to annoy your colleagues with your emails:
Change the subject line every time you start a new conversation. The email subject line should tell the reader what the message is about. So if an email strand about “next Thursday’s meeting” suddenly morphs into a discussion about “Mary’s retirement party,” consider changing the subject line. Having descriptive subject lines helps people quickly scan their inbox to decide which messages to read first and also helps when searching for a message after a conversation has ended.
Don’t use email when another medium makes more sense. Use email only when it's the best method. In many work cultures (like at Yahoo!), instant messaging is popular for quick conversations and sending links back and forth. If you know a colleague is on the road a lot and more likely to see a text message than an email, then use text messaging. If you know someone is at her desk and might not check an email about a meeting change in half an hour, the old-fashioned land line might be the best choice.
Answer questions inline. When someone sends an email asking several questions, train yourself to reply inline, inserting your answers directly beneath each question. (Hat tip to Gina Trapani).
Don’t get the last word in. There is usually no reason to cap off a long exchange with "thank you" (and certainly, "you're welcome"). An email conversation has to end at some point.
Use the cc function sparingly. Try to cc only those who need to know and avoid cc-ing long lists of people unless it is important that everyone know who else received a message. Certainly don’t use the cc function if you don’t want people on the list to know the names of the other people receiving the same message.
Keep it brief. When was the last time you read a work-related email and wished it was longer?
Say no to chain letters and jokes. While the rare forwarded email evokes a smile or a warm feeling, they are mostly irritating. And while you expect those emails from your batty aunt, you don’t want to be getting them from professional contacts.
How to Improve Your Email Etiquette [Yahoo Shine]