XADM: Cannot Disable Proxy Address Generators

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You cannot control the generation of proxy addresses for imported recipients or newly created recipients. For example, when you create or import users, the Microsoft Exchange Administrator program automatically generates an X.400, a Microsoft Mail, and an SMTP proxy address for each mailbox. You cannot force Exchange Server to generate only one or two of the proxy addresses. The Administrator program generates all three proxy addresses.

This behavior is by product design.

To find these addresses, click the Configuration container, open the Site Addressing Container properties, and then click the Site Addressing tab. The Remove button on this page can be used to remove a specific address type from all existing mailboxes, but Exchange Server will generate all types of address for new or imported mailboxes.