Today we got the executive green light to proceed with changing from a Domino platform to Exchange. The business prefers Exchange for a messaging platform. (even though IMO IBM Domino is fine - if it aint broke, don't fix it but it was not my call).

I have been put in charge of Domino to Exchange process goes smoothly as possible. I have also been told to put together costs for this project. I have some questions and concerns re: network design, licensing, costs:

The current setup is as follows.

1 HQ office (100 users), 1 secondary office (50 users), 5 branch offices (under 10 users).

• 5 different email domains
• Windows Server 2003 functional level with a few 2008 R2 Servers
• Lotus Domino Notes Servers (one in each office)
• Ironmail Appliance
• Public Domino Web Mail server
• Majority G5+ Proliant Servers
• Domino Blackberry Enterprise license and server
• No VoIP phones

What are the basic hardware requirements for Exchange 2007 or 2010?
Can I simply purchase a single physical server? Will each office require an Exchange server or possibly additional servers (roles)?
How is email routed to the smaller branch offices?
Standard or Enterprise licenses?

The business has been running Domino (messaging and application services) for over 10 years and also want Exchange to support email services, Blackberry, Outlook Web Access, possibly support for iPhone devices.

Thank you Serverfault universe.