When do you use the To: field or the Cc: field?? There really are no hard and fast rules. One of the words I use most here on this site is discretion — and when to use the To: field vs. the Cc: field is all about discretion and the circumstances at hand.
As a general guideline, use the To: field if you want to address several contacts for the same reason as a group, while encouraging their input. If you are listed in the To: field know that your input is being sought.
The Cc: field is generally used to keep others involved in a conversation in the loop (FYI) with no expectation of a reply being required. That is unless you are the one who is Cc:’d and have something important to add to the conversation that needs to be pointed out. In that case reply only to the Sender and do NOT hit Reply to All.
One concern stressed by those who email me is the unfortunate situation of having an email conversation with one party who then takes the liberty to Cc: others on their reply or mid-way through the conversation. For example two managers discussing their respective team’s responsibilities. One can see how one manager’s choice to Cc: the other manager’s staff about their opinion on the situation, can be perceived as a breach of confidentiality or encroaching on the other manager’s authority.
Cc: must be used with discretion. Only Cc: those who really “need” to be in the loop on your ongoing communications because it includes or effects them directly. Especially when when mixing internal and outside company contacts. Your employer’s business practices and methodologies should be protected and not exposed to outside parties in the guise of customer service (or worse yet your attempt to CYA). If you are unsure who should be Cc:’d run it by your manager or supervisor first.
To arbitrarily bring others into a private conversation when the person on the other side may not agree with that choice can cause misunderstandings and lead them to not trust that they can in fact have candid communications with you.
Be sure the other party doesn’t have an expectation that what you are discussing is between the two of you. It is the sign of a true professional to know intuitively when that is the case. One thing is clear — you should never play politics with these fields. Doing so will never be a successful strategy and can lend to you being perceived as trivial and/or unprofessional.
The bottom line?
Use the To: field for those who you desire to have a conversation with and want to encourage their input.
The Cc: field is best used in new conversations and is used to FYI without an expectation of a reply or additional input. Now here’s the important part — if you need to simply inform others about the outcome of the topic at hand — discuss this first with those already involved and start a new email that includes all involved.
By keeping these tips in mind you’ll be known as a courteous and efficient communicator and more importantly someone others can bank on to use their discretion when required.