Exchange Server Comparisons
As the Microsoft Exchange Server platform has continued to evolve over the years, it has changed from the typical all-in-one message server to a more distributed environment.
Exchange Server 2003
Exchange Server 2003 offered the following distributed server roles; some of these server roles were more difficult if not impossible to virtualize:
Front-end server This is responsible for external client connectivity (Outlook Web Access, POP3, IMAP, RPC/HTTP, SMTP, and Outlook Mobile Access, to name a few). This server role was easy to virtualize because it wasn’t very demanding on storage resources, and the VMware platform provided more than adequate CPU, memory, and network resources for these roles to perform as well ...