Our phones are of the "expandable handset" variety and they have an intercom feature.  It is nice, but we really don't use it all that much. 

As for email... for everyone to check the same email, and see what others have done, I would think that you would need to use some sort of web mail that you can all log into at the same time.  I don't think any email client will accommodate those needs.  An email client that runs on your computer (Outlook, Eudora, etc) all download the email from the server.  Web mail on the other hand, works with the email on the server.

Best,
Robert A. Franco
SOURCE OF TITLE