How to give permission to user to send email to mail group on Exchange Admin Center Login to Exchange Admin Center web link https://mailserver/ecp Go to recipients , then groups then select a group that you want to give a user permission to send email to. Go to delivery management , here Click Plus sign to add a user to give permission to send email to this group. The default option is ‘Only senders inside my organization’ .and there is other option to make a group to receive external emails as well,