When writing emails, there are several guidelines that should be followed at all times:

• Never write in all caps.  Normal sentence case must be used at all times, considering the email is a replacement for a letter.
• Make sure all emails are proof read and checked for any spelling or grammatical errors.  If necessary, write the email in Word first to allow you to run the Spelling and Grammar checker before copying into the message
• Double check the email address you have entered to ensure you have the details for the correct recipient, especially if the information is confidential 
• When using attachments, ensure they are not too large as this will increase the time taken to open / download the message.  If in doubt or attaching several files, zip them before attaching.  Alternatively, you could share the file(s) via cloud storage.
• Never write an email when you are angry.  This will often lead to inappropriate message where you will regret your words later.
• Ensure a meaningful but brief subject is included in the email.  Never leave it blank as some people may have a policy never to open emails without a subject.  Similarly, do not use "Re:" or headings that are similarly meaningless.
• Always include a greeting.  Use words such as "Hi" or "Dear" followed by the recipients' names
• Use short, concise paragraphs
• Always include a closing paragraph containing the requested action related to the email.  This could include "look forward to hearing from you" or something similar
• Always include a good will message at the end of the email and follow this by your name / signature.  This is polite and the person may not be able to directly identify you from your email address
• All business emails should be sent using your business email address which can clearly identify the organisation with whom you are employed.  Do not use personal email to send an email to a business associate.  This may be inappropriate in the name used within your email address.  
• Do not send joke emails to people in the office via business email.  This can become distracting and very annoying and is generally inappropriate.