As of August 4th 2014 Microsoft will be ending its support for Microsoft Exchange 2003.
If you are using Microsoft Exchange 2003 and want to have support for Microsoft Exchange products, then you have to start thinking how to upgrade your Exchange environment to newer version Exchange 2007 or 2010.
After August 2014 Exchange 2003 will not be supported by Microsoft anymore.
All Microsoft Exchange Product Lifecycle information Table can be found here:
Microsoft Exchange Support Lifecycle