What does Cc: stand for? Back in the stone age, when typewriters were all the rage, carbon paper was used to make an identical copy of the typed letter.
You would put two pieces of paper with a sheet of carbon paper in-between to type your communication on. The Cc: noted at the bottom of the letter let the person the letter was going to know who would get that “carbon copy.”
Speaking from experience, it was a real pain when you made a typo! Email Cc: is referred to as “Courtesy Copy” because there is no real hard copy to send.
I’ve been Cc’d – what should I do?
Unless the Sender specifically asks for your input, a response is not necessarily required. By being Cc’d, you are FYI’d while being allowed to comment. But… here is where discretion is essential!
You need not respond if there is nothing to say. One example would be 
if you were sent meeting minutes. Unless something is wrong or omitted – no response is necessary or expected.
Say you were Cc’d on an email with many other folks noting that a meeting time had been pushed out or changed. In that case, I would reply with a “Thank you for the update – I’ve changed my calendar accordingly and look forward to…”. In addition, I would want to know that folks got the reschedule note and are good to go if I sent that email.
No need to reply if there is no need to reply.
Unfortunately, I’ve seen onliners who need to reply when they are not adding anything valuable to the conversation. In other words, no need to respond just to type “okay.”
Or they hit “Reply to All” and make comments that are not pertinent or of interest to the others who were also Cc’d. Remember, when you see a list of folks being Cc’d, feel free to prune that list if your comments only apply to the original Sender.
Discretion means “the ability or power to decide responsibly.” That applies to everything email because you’ll always need to decide what actions to take – or not take responsibly.
Use To: or Cc:?
When do you put your email addresses in the To: field or the Cc: field? Unfortunately, there are no hard and fast rules – you have to use your discretion based on the circumstances at hand.
As a general guideline, use the To field to email several contacts while encouraging their response. A response is expected when your email address is in the To: field. Only when your comments are essential to the group would you use Reply to All.
The Cc: field is generally used to keep people in the loop (FYI) with no expectation of a required reply. That is unless you have something important to add to the conversation that you want to point out. In that case, reply to the Sender only and do not hit Reply to All. Instead, let the Sender decide to send your reply to the others involved.
One thing is clear – refrain from playing politics with these fields. Using these fields to make someone feel less important or make a point by putting them in the Cc: field when it would make sense to include them in the To field is incorrect. Doing so is never a successful strategy and can backfire, making you look trivial.
The Bottom Line if You are Cc’d
When you are, Cc’d, respond only if you have commentary that you know is necessary to the ongoing conversation or topic. If you have a question about the email, now is the time to ask.
Also, be sure to take the time to check who else is in the To: and Cc: fields. If any, only keep those addresses that are part of the ongoing conversation and need to be aware of your reply. Trim the unnecessary email addresses out before hitting Send.
These minor considerations take only a bit of your time and can go a long way to being viewed as a proficient and tech-savvy emailer.