Hello, @Roger Roger,
Welcome to the Microsoft Q&A platform!
Based on your description, I understand that you want to know if it is possible to disable or remove email addresses to prevent all members of an O365 Unified group from sending or receiving email.
While there is no direct way to completely remove an Office 365 group's email address, you can effectively disable it by combining the following methods to ensure that the group is unable to send or receive email.
1.You can hide the group from the Global Address List (GAL) and other address lists by using Set-UnifiedGroup in PowerShell. This way, users won't be able to find the group in Outlook or Outlook on the web. The specific command and its parameter are as follows.
Set-UnifiedGroup -Identity "GroupName" -HiddenFromAddressListsEnabled $True
2.You can use Set-UnifiedGroup cmdlet in PowerShell to block users from sending or receiving emails from the group's address. The specific command and its parameter are shown below.
Set-UnifiedGroup -Identity "GroupName" -RejectMessagesFromSendersOrMembers @{Add="Sender1","Sender2"}
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Thank you for your support and understanding.
Best Wishes,
Alex Zhang