Other features include:

• Up to 16 GB per mailbox database and up to 20 mailbox databases per server
• Multiple message databases per server running Exchange for fast backup and restore, flexible data management, and increased reliability
• Organizations do not have to upgrade or migrate overnight Exchange 2003 operates with Windows 2000 or Windows Server 2003 and coexists with Exchange 5.5 and Exchange 2000, all within the same topology
• Exchange 2003 also operates with Microsoft Office Outlook 2003, Outlook 2002 (Office XP), and Outlook 2000. Outlook Web Access can be used on other client platforms through browsers
  
   
• Secure defaults (for example, Simple Mail Transfer Protocol [SMTP] relay, Post Office Protocol 3 [POP3], and Internet Message Access Protocol [IMAP] are turned off by default)
• Improved ability to restrict connections and e-mail messages
• Support for Outlook Web Access automatic logoff, Secure/Multipurpose Internet Mail Extensions (S/MIME), HTML, and attachment blocking
• New antispam features and integration with Office Outlook 2003 Safe and Block Sender lists
• New Virus Scanning API 2.5 for improved antivirus solutions
• Support for Windows Server 2003 Internet Information Services (IIS) 6.0, which isolates applications
  
   
• Multiple database architecture enables new consolidation opportunities for users of Exchange 5.5
• Enhanced administrative tools for mailbox management
• New client logging and error reporting tools for faster problem resolution
• Integration with Windows Server 2003 Volume Shadow Copy service for fast, reliable backup and restore
  
   
• New, enhanced Outlook Web Access for fast access to Exchange from the Internet and with greater security. The new user interface (UI) is updated to mirror the Outlook 2003 UI and includes new features such as spelling checker, tasks lists, S/MIME support for security, and HTML content blocking for security
  
   
• Windows powered mobile devices can synchronize directly with Exchange 2003 for enhanced security
• Integrated support for HTML, Extensible HTML (XHTML), Wireless Application Protocol (WAP) 2.x, and compressed HTML (CHTML) mobile microbrowsers
  
   
• Enhanced performance and Exchange Cached Mode enables use over low bandwidth as well as over latent and poor network connections
• Improved UI enables users to prioritize overloaded Inboxes
  
   
• Improved virtual memory management
• Improved Outlook performance logging to the server
• Faster cluster failover times with Windows Server 2003
• Support for four-node and eight-node clusters
• Support for Windows Server 2003 IIS 6.0, which isolates applications
• New resources and prescriptive guidance on deployment
• New premigration analysis and reporting tools
• New Active Directory Migration Tools (ADMT 2.0)
• Active Directory Connector Wizard
• Internet Mail Setup Wizard
• Mailbox and public folder migration tools
• Eight-way clustering