Add in a filter for outlook

If you log on in portal.office.com and check your email, there is a Filter option so you can also change your view (to conversations)

Filters--> View--> Conversation

Customers who are accessing their mail through workspace get a bare outlook view where one cannot change their settings. So they get each reply in a seperate mail. If there has been an attachment a few comments back it can be a pain to find it again.