Open Active Directory.
Navigate to the folder where you want to create your contacts, right-click the folder, point to New, and then click Contact.
On the New Object page, complete the name information, and click Next.
On the next page, verify that the Create an Exchange e-mail address check box is selected.
In E-mail address, click Modify.
In New E-mail Address, select the e-mail address type for the target address. In this example, select SMTP Address, and then click OK.
In Internet Address Properties, type the e-mail address that is used by your external recipient. type @externaldomain.com, and then click OK.
Complete the wizard to create a contact with the proper target address.
Right-click the contact, and click Properties.
Click the E-mail Addresses tab, and select the SMTP address of the parent company, in this case, @externaldomain.com. Click Set As Primary.
You can then forward the messages to this contact.
