SendAs permissions granted to users in forests are not visible in Send As Permission Wizard in EMC
Original KB number: 2401524
Symptoms
The Send As permissions that are granted to users in forests trusted by Exchange Server forest aren't visible in the Send As Permission Wizard in Exchange Management Console (EMC).
Cause
It is the current design in Exchange Server 2010.
Workaround
To view all accounts that have SendAs rights on a mailbox, you can use the following PowerShell command instead:
Get-ADPermission <mailboxname> | where {($_.extendedrights -like "*send-as*") -or ($_.accessrights -like "*Generical*")} |fl *
For more information, see Manage Send As Permissions for a Mailbox.