Assuming there exists a user with a laptop that is not part of the domain, is it possible for an Outlook 2010 on this machine to access mailbox, calendar and the rest associated with the user's mailbox on an Exchange 2010 server? OWA is a solution, but given the significance of the user, it would be very handy if the same could be achieved with Outlook 2010 and without his laptop joining the domain.
The computer Outlook 2010 is running on doesn't have to be a member of the domain (or any trusted domain of the forest) where Exchange 2010 is installed. As long as Outlook can resolve the name of the Exchange Server computer alright the user will be prompted for credentials for the mailbox by Outlook when they attempt to open the mailbox.
For me, name resolution has been the sticking point in most situations like this. Outlook actually handles the situation very effectively.
What you looking for is called RPC over HTTPS. It's a way that Outlook 2003/2007/2010 can connect to Exchange 2003/2007/2010 without being part of the domain. You would require SSL certificate to accomplish it though. There is a different requirements, if outlook connects from outside the network, such as over INTERNET or from the same LAN. Well, it's not really a REQUIREMENTS per-se but different name resolution will be required to properly connect.