For outgoing email, you should be able to turn on archiving and set a recipient (I believe it is now called "Journaling"). As for the duplicate incoming email issue, that's much more complicated. Generally in this circumstance, you take these actions because you want to keep a copy of all emails that somebody received for internal policy or regulation compliance. To do this, you need to show that not only was it sent to somebody, but the individual actually received it if it were contested by the employee or other party. Keeping a single copy of the message sent to everybody would not meet this.
If you really need only a single email copy, you will likely have to work with 3rd party filters and plugins/event sinks/etc.
