Get list of delegated mailboxes and delegates in Exchange 2010\2013

Sometimes you will need to get a list of users (delegates) that have access to other mailboxes (delegated mailboxes). Exchange 2010/2013 provides Get-MailboxPermission cmdlet that can query mailboxes for permissions. 

You can extend use of cmdlet to all mailboxes:

Get-Mailbox | Get-MailboxPermission

There will be a lot of permissions including SELF and inherited. We will filter them:

Get-Mailbox | Get-MailboxPermission | where {$_.user.tostring() -ne "NT AUTHORITY\SELF" -and $_.IsInherited -eq $false}

You can export the list to csv-file and open it in Excel (first string) or to get quick analysis, export to separate table (second string):

Get-Mailbox | Get-MailboxPermission | where {$_.user.tostring() -ne "NT AUTHORITY\SELF" -and $_.IsInherited -eq $false} | Export-Csv c:\mailbox-permissions.csv

Get-Mailbox | Get-MailboxPermission | where {$_.user.tostring() -ne "NT AUTHORITY\SELF" -and $_.IsInherited -eq $false} | Out-GridView

In this way you can audit if you have extra-delegated mailboxes or you can find out to what mailboxes particular user have access.