Office 365 - Set send-as/send-on behalf of a Group
There may be times when you need to have the ability to either send-as or send-on behalf of a group you are a member of. If you need one of these permissions to a group, follow the steps below to make this request.
Note: You must be the Group owner to make this change. If you are not the Group owner, contact the Group owner.
Set send-as/send-on behalf of a Group
As the Group owner, follow steps outlined in managing group settings/preferences article.