Is there a halacha or other rabbinical consensus concerning a sole recipient of an e-mail forwarding the message to another person? I ask this question in the context of business. I recently received an e-mail from a supervisor who gave directions that involved other people. Would there be any ethical, moral or legal violation if I were to send the other parties a copy of the e-mail?
from http://www.torahmusings.com/2013/02/keeping-secrets/, by Rabbi Ari Enkin, citing Yoma 4b