You do not need to go to Exchange 2000 first -- you can install new HW/SW (E2003/Windows 2000 or Windows 2003), set up the Active Directory connector (using the new ADC tool) and move Exchange 5.5 mailboxes to Exchange 2003. If you want to re-use your existing Exchange 5.5 HW, you can repurpose the original Exchange 5.5 HW, after all mailboxes are moved off of it, by reformatting and installing Exchange 2003/Windows 2000 or Windows 2003. SearchWin2000.com: Can you move mailboxes between an Exchange 5.5 organization to an Exchange 2003 organization?
Yes. You can use the Exchange System Manager to move mailboxes from Exchange 5.5 to Exchange 2003, which provides a faster and more reliable upgrade. Microsoft also provides three tools to facilitate migration to and from Exchange 5.5 and Exchange 2000 (applies to Exchange 2003): the Move Server Wizard, Exmerge and the Exchange Migration Wizard (for Messaging Application Programming Interface [MAPI] migration). Knowledge Base article Q281584,
Front-end is outside the corporate firewall -- back-end is inside the corporate firewall. A front-end server is a server that receives requests from clients and relays them to the appropriate back-end server. A back-end server is a server that hosts at least one database to which front-end servers connect when relaying requests from clients. SMTP gateways are servers that route e-mail messages through an organization or the Internet to their final destination.
David Madison is a program manager in the Exchange server product unit. That group is responsible for developing customer deployment requirements for Exchange as well as running Exchange early adopter programs. David has been with Microsoft for over 10 years, working on all of Microsoft's messaging technologies, from MS Mail up to Exchange 2003 SearchWin2000.com: There seems to be many features that will be dependent on Outlook 11, but what features will be dependent on Windows 2003 Server?
The Exchange Server 2003 features that require Windows Server 2003 are 8-node clustering, Volume Shadow Copy Service, RPC over HTTP support, memory allocation, Active Directory improvements, Mount Point support with clusters, IPsec support for front-/back-end clusters and Cross Forest Kerberos Authentication with Outlook 11. The features that require Outlook 11 and Exchange Server 2003 are MAPI over HTTP, reduction of client/server traffic due to better data compression, and the Outlook 11 performance monitoring features that are collected by Exchange Server 2003.