Ok, normally in a business situation you would think that emails, or any type of correspondence for that matter, would be professional.  But sometimes that’s not the case and in some industries, like customer service for example, they get more than their share of rude emails.  So how do you handle it without losing your cool?

Don't Answer Them Right Away

Come back to them later, after you've had a chance to let them sink in, and they probably won't anger you quite as much. You'll stop dwelling on the email problem, send nicer responses back, and be able to move on with your day more effectively.

Kill Them With Kindness

Unfortunately, some people are just stubborn and will be a jerk either way. In those situations, the best thing you can do is cool off, answer their email as kindly as you can, and move on to your other messages.  Again, make sure you're as polite as possible in these situations, because if you let yourself get angry, you're giving legitimacy to their rudeness.

Find more ways to deal with this problem here.