After a recent office 365 update a few users 'Sent' folder is missing in Outlook. Normally they would have Inbox/Draft/Sent/Deleted but outlook only shows Inbox/Draft/Deleted. now. scanpst as well as the Microsoft Support and Recovery Assistant. I then tried to delete the profile and tried outlook in safe mode. That Sent folder seems to be gone. Cached was turned off, the "keep a copy of sent items in sent folder" is enabled.
Outlook on the web and the same user on a different pc seems to follow the profile. However the sent folder is present on the phones of those that have an iPhone.