Hi Max,
You can follow the steps to check the ‘Retention Policies’.
1.Logging into Office 365 mailbox via the following URL
2.Click ‘Options’ on the top right and then select ‘See All Options’.
3.Choose tab ‘Organize E-Mail’ and click ‘Retention Policies’.
Please check whether there are contents. If you can, please post a screenshot.
Thanks,
Ray Yang