Get All Mailboxes With Permissions Other Than ThemselvesGet All Mailboxes With Permissions Other Than Themselves. Here's how:
Get-Mailbox | Get-MailboxPermission | where {$_.user.tostring() -ne "NT AUTHORITY\SELF" -and $_.IsInherited -eq $false} | Select Identity,User,@{Name='Access Rights';Expression={[string]::join(', ', $_.AccessRights)}} | Export-Csv -NoTypeInformation mailboxpermissions-v1.csv