Find mailboxes hidden from the GAL using Powershell

We can easily get the list of all mailboxes that are currently hidden from Global Address Book using the Exchange Powershell cmdlet Get-Mailbox. The Get-Mailbox cmdlet includes the property HiddenFromAddressListsEnabled and this property indicates whether the mailbox is hidden from GAL or not. So we can query the mailboxes with where filter by checking whether the property HiddenFromAddressListsEnabled is set to true or not.

Get-Mailbox -ResultSize Unlimited | Where {$_.HiddenFromAddressListsEnabled -eq $True}

You can run the following command if you want the output consist of only selected properties :

Get-Mailbox -ResultSize Unlimited | Where {$_.HiddenFromAddressListsEnabled -eq $True} |
Select DisplayName,UserPrincipalName, HiddenFromAddressListsEnabled

We can also export all the hidden mailbox users to csv by simply using Export-csv cmdlet:

Get-Mailbox -ResultSize Unlimited | Where {$_.HiddenFromAddressListsEnabled -eq $True} |
Select DisplayName,UserPrincipalName, HiddenFromAddressListsEnabled |
Export-CSV "C:\Hidden_MailBoxes_GAL.csv" -NoTypeInformation -Encoding UTF8