Hi,@Mytoast Admin
Thanks for posting your question in the Microsoft Q&A forum.
You want to access M365 group mailboxes, mail-enabled security group mailboxes, and public folder mailboxes through PowerShell. What information do you want to check in your mailbox?
The following is the cmdlet for querying basic mailbox information.
1. Returns information about all Microsoft 365 groups, display names, email addresses,Owners and Privacy.
Get-UnifiedGroup | Format-List DisplayName,EmailAddresses,ManagedBy,AccessType
2. This example show the members of the Microsoft 365 Group named Group2.
Get-UnifiedGroupLinks -Identity "Group2" -LinkType Members
3. Access the mail-enabled security group mailbox named "Test5/30".
Get-DistributionGroup -Identity "Test5/30" | Format-List
4. Access the public folder.
Get-Mailbox -PublicFolder
If my answer is helpful to you, please mark it as the answer so that other users can refer to it. Thank you for your support and understanding.