Hi @tormod,
This has been reported by a number of users and filed as an issue on GitHub (Reduce the number of new submission notification emails for editors, and simplify their management · Issue #3770 · pkp/pkp-lib · GitHub). It’s scheduled to be fixed in OJS 3.1.1-5. Feel free to follow progress or add your own comments to the issue.
Best,
Amanda Stevens
Public Knowledge Project Team