While you cannot customize the default welcome mail for Office 365 Groups, disabling the welcome mail is possible with an extra parameter in the Set-UnifiedGroup cmdlet in Exchange PowerShell: -UnifiedGroupWelcomeMessageEnabled:$false. See https://docs.microsoft.com/en-us/powershell/module/exchange/users-and-groups/set-unifiedgroup
Use this as a part of a custom group creation flow if you would like to restrict and/or customize the welcome mail for many groups across your tenant.Anonymous commented
does the disabling of the welcome message also work for guests?
Apologies for the previous irrelevant admin response. We’re still thinking about this one.
We have announced that Group Owners will be able to leverage existing groups to drive membership in Office 365 Groups.
We’re working on the ability to change the SharePoint site URL associated with an Office 365 Group.