I'm trying to write a powershell script to list (and remove) the AlternateMailboxes from an Exchange account. I found a few examples to get this list by querying all users in Exchange and matching those user's mailboxpermissions with the account I want to check, but with an Exchange Organization with more than 50.000 mailboxes, it takes forever to get this list of permissions.
I know Outlook 2010 can get this list in just a second, by querying the Autodiscover webservice, which returns an xml with all the AlternateMailboxes listed for a user. I wonder where this autodiscover service gets this information. I searched the AD and Exchange properties of a user/mailbox, but I cannot find a property containing this list of AlternateMailboxes. Where can I find this list (without using special functions to query the Autodiscover webservice)?