If you want to uninstall office exchange server, you need to follow the given process,
But, You cannot uninstall Exchange Server 2003 from a server
If it is the only server in a mixed administrative group that is running Site Replication Service (SRS)
If it is a bridgehead server for a connector and there are other Exchange servers in your organization.
If it is the routing master and there are other Exchange servers in your organization.
Get office 365 or Office 2016 setup here : office setup
How to Uninstall Exchange Server 2003?
Log on to the server from which you want to uninstall Exchange.
Click Start, point to Control Panel, and then click Add or Remove Programs.
In Add or Remove Programs, select Microsoft Exchange, and then click Change/Remove.
On the Welcome to the Microsoft Exchange Installation Wizard page, click Next.
On the Component Selection page, in the Action column, use the drop-down arrows to select Remove, and then click Next.
On the Installation Summary page, verify that the Action column is set to Remove, and then click Next.
On the Completing the Microsoft Exchange Installation Wizard page, click Finish.
For more details, visit : www.office.com/setup