This issue occurs when you make this change on the General tab in the Group Properties page in the Active Directory Users and Computers snap-in.
The problems that may occur include the following problems:
- Duplicate SMTP e-mail addresses may be created. Additionally, two users may have the same SMTP e-mail address.
- The primary e-mail address may be overwritten by the secondary e-mail address.
- You receive the following error message:
The selected recipient is already mail enabled.
- If you change the global SMTP site address in the Microsoft Exchange Administrator program, the SMTP address of some custom recipients may not change to match the new site address.
- When you create a custom recipient and add a secondary proxy address that is the same type as the target address (SMTP, X.400, or MS), the target address field is replaced by the secondary proxy address field.