Sometimes CC-ing a co-worker’s supervisor as a way of tattling or intimidating is necessary but it should only be used in extreme circumstances because it tends to create a hostile work environment. That’s not good for anyone.

Rampant CC-ing leads to rampant Reply All-ing (another office no-no) sending everyone down a never-ending email rabbit hole until people start revolting and demanding to be taken out of the email chain. It’s generally a bad idea to use Reply All at work if possible. How many times have you dashed off a response, hit Reply All only to realize you hadn’t seen every name on the list and you’ve just made an embarrassing faux pas. Take the extra two seconds to retype the addressees so you know exactly who you’re messaging.