Internal e-mails not showing email address

Hi Everyone.

I'm managing a hosting Exhcange 2010 environment that has more than one domain, much more.

The issue I'm having is this. Suppose we have to companies A and B, which both happen to be our clients.

If John Doe from Company A would happen to send a mail to Richard Roe from company B, Richard's mail client will display the "From" field as "John Doe" only - without the email Address.

This is a problem because the companies aren't related in any way - they simply sit on the same Exchange server.

Another issue that's caused by this behavior include mails forwarded to external addresses - meaning, supposing John Doe sends a mail to Jane Doe and they are both from the same company - the mail address won't show but that's not really a problem - but if Jane was to forward that mail to a third party - which is not hosted on the same server - the third party would see Jane's mail address but not John's and if they need to answer John's question that might've been redirected through Jane - they won't be able to do so as they don't see his email address.

In short - I need to configure my Ecchange server to show the sender's email address on all mails.