**As** an OpenProject user
**I want** to receive an email notification when the due date of a work package (or a custom field of type date) is approaching Begin of the insertion(or is overdue)End of the insertion
**so that** I do not forget important deadlines.

**Use case (example)** Begin of the insertion

* End of the insertion Begin of the deletion

-End of the deletion A ticket of type bill or invoice has been created and needs to be paid. The user can easily forget to pay the bill if not reminded.

**Acceptance criteria** Begin of the insertion

* End of the insertion Begin of the deletion

-End of the deletion Timeframe for reminder should be configurable. Begin of the insertion
* End of the insertion Begin of the deletion
-End of the deletion Reminders should be sent for both end dates of work packages and custom fields of type date. Begin of the insertion
* End of the insertion Begin of the deletion
-End of the deletion For custom fields of type date it has to be possible to define whether a reminder should be sent (if a relevant end date is referenced) or not (e.g. when a start date is referenced).