Ask the Expert

Migrating OWA users from Exchange 5.5 to Exchange 2003

We are currently migrating from Exchange 5.5 to Exchange 2003. How would you recommend migrating Outlook Web Access (OWA) users? I realize that users migrated to the new OWA server could just use a different address, but I want to make the transition as seamless as possible for them.

Would you have the users continue to use OWA 5.5 to access Exchange Server 2003 until everyone is cut over, then switch everyone over to OWA 2003? I know OWA 2003 is not backward-compatible. Some articles I've read say OWA 5.5 can access Exchange Server 2003, and some say you can't.

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Detailed information on this topic is available from Microsoft: "Introduction to front-end and back-end topologies for Exchange Server 2003 and Exchange 2000 Server."

If you are in the middle of a migration from Exchange 5.5 to Exchange Server 2003, you need to wait and cut everyone over at the same time as you cannot access Exchange 5.5 mailboxes with the Outlook Web Access (OWA) 2003 interface.

The following table from Microsoft articulates the various options you have in this scenario:

Outlook Web Access versions available to users
Front-end serverBack-end serverOutlook Web Access version
Exchange 5.5Exchange 5.5Exchange 5.5
Exchange 5.5Exchange 2000Exchange 5.5
Exchange 5.5Exchange 2003Not supported
Exchange 2000Exchange 5.5 Not supported
Exchange 2000Exchange 2000Exchange 2000
Exchange 2000Exchange 2003Not supported
Exchange 2003Exchange 5.5Not supported
Exchange 2003Exchange 2000Exchange 2000
Exchange 2003Exchange 2003Exchange 2003

Outlook Web Access was changed significantly along the various releases of Exchange Server. Even the Exchange 2007 OWA experience has more advanced features and functionalities than its predecessors.

Do you have comments on this Ask the Expert Q&A? Let us know.

Related information from

  • Expert Advice: Migrating multiple locations from Exchange 5.5 to Exchange 2003
  • Expert Advice: Some accounts can't log onto OWA after migration
  • Tip: Preparing for an Exchange 2003 upgrade
  • 11 tips in 11 minutes: Migrating from Exchange 5.5 to Exchange Server 2003
  • Learning Guide: Exchange migration
  • Reference Center: Exchange migration advice and resources
  • This was first published in June 2006

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