1.       Extend the Active Directory schema for Exchange Server 2003. Run ForestPrep  in forest level.
2.       Configure a Global Catalog Server in the Child Domain
Log on to a domain controller.
Click Start, point to Administrative Tools, and then click Active Directory Sites and Services.
Expand Sites, expand Default-First-Site-Name (where Default-First-Site-Name is the name of your site), expand Servers, and then expand a domain controller from the child domain where you want to install Exchange Server 2003.
Right-click NTDS Settings, and then click Properties.
Click to select the Global Catalog check box, and then click OK.
Quit Active Directory Sites and Services.
Run the Exchange Server setup /domainprep command again in the child domain.
Restart the Exchange server, and then run Setup to install Exchange Server 2003.
3.       Exchange Administration Delegation
1.       Click Start, point to Programs, point to Microsoft Exchange, and then click System Manager. 
2.       Right-click the organization or the administrative group where you want to delegate administrative permissions, and then click Delegate control. Exchange Administration Delegation Wizard starts.
3.       Click Next. 
4.       On the Users or Groups page, click Add.
5.       In the Delegate Control dialog box, click Browse.
6.       In the Select Users, Computers, or Group dialog box, click the appropriate location in the Look in box, click the name of the user or the group that you want to add, and then click OK.
4.       Prepare the domain for Exchange Server 2003. Run DomainPrep  in domain level.
5.       Install Exchange Server 2003. Run setup.exe.