I see there where plenty of sites/blogs explains how to convert an Office 365 group to a Teams. Super easy to change it using Teams client. I did not see any reference to other way around. If you find this blog, Good for you.
I see few users created “Teams” in Teams client. They wanted to use the Office 365 group mailbox for that Teams. With Client side settings, there is no options to do that at all. As an Exchange Administrator you can do it in PowerShell.
For every “Teams” created in Teams client, you will see an “Unified Group” aka “Office 365 Group” in Exchange. So all we have to do is change is unhide this Office 365 group for Exchange Outlook users. Here is how you do it (Make sure you connect to Exchange Online first) in PowerShell:
# Replace "TeamsName" with your name of the Teams in double quotes
Set-UnifiedGroup -Identity 'TeamsName' -HiddenFromExchangeClientsEnabled:$false -HiddenFromAddressListsEnabled:$false
After you set to False to both properties, The Teams will show up in Outlook under Groups in Mailbox tree if they are members. Give it plenty of time ( 30 mins ) to take effect of this setting change.
Did it help you? leave me a comment.
Anand, the Architect 