Work Emails: You should always remain professional when sending emails through a work email address. This is not the time to let the office know how funny you are. Avoid using all caps, smiley faces, and excessive explanation points. This comes across as childish and unprofessional. When at work, never assume your emails are private. Be sure whatever you are writing is something you would be able to say to the office. You never know who that email may be forward to on accident or on purpose.
All Emails: Be sure you are using proper grammar. You never want to come across as lazy or unprofessional. Refrain from hitting respond all whenever possible. Nothing is more annoying than being copied on an email you didn't even care about in the beginning, but now all 75 people copied are now replying all.
When forwarding an email be considerate of people's email addresses in the body of the email. Email addresses are just as personal as giving out a phone number so the same consideration should be made. Use BCC (blind carbon copy) to help protect your contact's email addresses.
Stop being lazy about emails. Nothing is a quicker turn off than a lazy email. Stop emailing like a text.
Always remember that an email is forever! Think twice before hitting send button.
Never too late to Right a Wrong:
If you do send an email you should't have or that you regret sending, just own it. Face it and apologize to try and make the issue right. Because an email can always be pulled up, you will just get yourself into more trouble if you to deny or lie your way out of the situation.