Within a secure messaging environment, a determination is made that a request to send a message has been generated by a message sender. A message protection policy configured to process the message within the secure messaging environment is identified. The message protection policy specifies that, within the secure messaging environment, a secured digital certificate, other than a digital certificate of the message sender, is configured with an associated private key to digitally sign the message on behalf of the message sender. Based upon the message protection policy, a determination is made to digitally sign the message using the private key of the secured digital certificate. The message is signed on behalf of the message sender using the private key of the secured digital certificate.