Limit @mentions and share feature to specific groups

We use our Confluence wiki for internal communication and to work with our customers in specific projects.

After the last upgrade to Confluence 5.1.4 we received several emails from our customers that the get a warning/error from our mail server after they shared a page or used an @mention.

This is true cause our Mailserver does not allow relaying for other mail domains!

http://en.wikipedia.org/wiki/Open_mail_relay

So we actually have 2 options:

1) deactivate @mentions completly
2) to live on with this mailserver warning/errors.

But number 2 isn't quite an option.

It would be best if we could limit this feature to a specific group of people.

Kind Regards
René

P.S. The same goes for "share pages"