Forum Discussion
365 Groups "Full Teamsite" & External Sharing
You can change the default using PowerShell.
From https://support.office.com/en-us/article/Manage-external-sharing-for-your-SharePoint-Online-environment-c8a462eb-0723-4b0b-8d0a-70feafe4be85?ui=en-US&rs=en-US&ad=US:
"By default, all SharePoint site collections that are part of an Office 365 Group have the sharing setting set to Allow sharing only with the external users that already exist in your organization’s directory. To change this setting, you can use the Set-SPOSite Windows PowerShell cmdlet."
AFAIK, for First Release tenants, modern SharePoint Online team sites have already come to all existing Office 365 Groups ...
MicrosoftThanks for the feedback everyone. For group connected sites, the default sharing setting is to enable sharing with existing external guests. This can be changed as noted earlier in the thread via PowerShell: