THIS ONE must have come as a surprise to you,but is taken seriously in the corporate world: Your boss told you to grow up because you used :p in an email.Indeed,email etiquette is a big deal,and you will end up hurting your own interest if you dont follow its rule

Keep in Mind the following things :

1 Plan the Email 

You shouldnt put anything in an email that you wouldnt put on a postcard.A client usually signs a confidentiality agreement when engaging a company.One should always remember that e-mails are company property and can be used in a court of law, Email can be forwarded;an unwanted party may see what you have written.So avoid writing personal emails from your company email ID.
2 Mind your Language 

People have forgotten basic letterwriting skills.SMS language and writing the entire mail in capital letters is common..Remember,when you write using capital letters,it looks as if you are shouting.Most emails dont have a proper greeting.Make sure your mail includes a courteous greeting and closing and always address your contact with the appropriate level of formality.

3 Check CCs and BCCs 

Use blind copy (BCC) only when sending the email to a large number of recipients.Copy (CC) only people directly involved.Also,be sparing with the reply all button.

4 Reply Quickly,be Brief 

Reply to important messages quickly.If you receive an emotionally charged message,take a minute to think it through and then reply.Try to concentrate on one subject per message.An email longer than necessary is quite frustrating.No one likes to scroll through endless pages of replies to understand a discussion,so try to summarise long discussions.

5 Dont Run,Dont Hide 

I think people should not use e-mail to cover up their mistakes.Work issues which put emotional pressure,should not be discussed over email.