Go to More > Preferences > Calendar & To Do > Display > Views and there set the options
Display To Do Entries and Display overdue To To items on the current day.
This enables an agent called "Updatetasks" in your mail file.
BUT: In 8.5.2 this agent is broken, as the agent security is not set correctly in that version.
It will not run...
You should update to 8.5.3, where this bug is fixed: as SPR: IFAY8AEEP6
For 8.5.2 there is a work around, but this requires designer access and a designer client: change the security setting of the agent in the template to 2 and then design update will resolve the issue.
If all of this is fixed, the admin of the server can still disallow running of agents... Then this will also not work.