PS C:\> Get-Mailbox | Get-MailboxPermission -User vasil
 
Identity             User                 AccessRights
 
--------             ----                 ------------
HuKu                 Vasil Michev         {FullAccess}
retail               Vasil Michev         {FullAccess}
sharednew            Vasil Michev         {FullAccess}
testplan2            Vasil Michev         {FullAccess}
WC                   Vasil Michev         {FullAccess}