Each product that Microsoft releases has a lifecycle that determines how long we maintain and support the product. Exchange 2003 mainstream support is over. And, Exchange 2003 extended support ends on April 8th, 2014. For more information about specific versions of Exchange 2003, see the Microsoft Support Lifecycle Search page, and enter “Exchange Server 2003” in the Product Name field.
Remember you cannot upgrade directly from Exchange 2003 to Exchange 2013 within the same Active Directory forest.
- Deploy an Exchange 2010 based hybrid in the Exchange 2003 forest and move mailboxes to Exchange Online
- Upgrade to Exchange 2010 and optioanlly from Exchange 2010 to Exchange 2013 within the Active Directory forest