Find Duplicate SMTP Address

Follow the Below Steps to Find the Dupilcate EMail Address in your Exchange Org

-----------------------------------------------------------------------------
The Active Directory Users and Computers snap-in can be used to search for the address. To do this, follow these steps:

1, Run Active Directory Users and Computers.
2, Right-click the domain object and choose Find from the context menu. This will
bring up the Find Users, Contacts, and Groups window.
3, In the Find drop-down list, choose Custom Search.
4, Click the Advanced tab and in the Enter LDAP query: field, enter the following
text: proxyaddresses=smtp:balgates@contoso.com
5, Click the Find Now button
---------------------------------------------------------------------------------------