Introducing 'Follow in inbox' and other improvements for managing group emails in Outlook

I ticked the "Subscribe new members" box but the user still wont recieve the emails send to the group in there personal Inbox, also removed members from the group and re-added them. So i need to tell a CEO of a company who is paying me big bucks to automate stuff for him that he needs to expand the group in his Outlook and needs to click a button to subscribe to the mailbox?
His first reaction was.. Hmm what's wrong with the old way.. And i can't blame him. So now i had to reconfigure al the groups that I "upgraded" (Ye Microsoft calls it an upgrade..) to a Office365 back to a distribution list.