Tip #5 All E-mails Are Forwarded
I have seen many e-mails where the original author obviously didn’t intend for the e-mail to be forwarded. And, the forwarder was not acting maliciously, but there was something in the thread that he or she thought should be shared with others. Unfortunately, the wording of the e-mail, especially those comments made about another colleague’s performance, character or personality were not so carefully crafted.
Avoid editorializing in emails. To be safe, just assume that your emails are so important that they will always be forwarded. By the way, telling some specifically NOT to forward an e-mail is not a foolproof solution either.