When you create a project in our instance of openproject, it sends an email to everyone assigned to it, as expected. However, if you add a note or otherwise modify a project, no one gets email. If OP was simply not sending emails at all this would be easier to troubleshoot in a way. As it is, I’m not even sure where to start other than to check all the notification-related settings I can find, which I’ve done.

In particular, everything in Admin -> Settings -> Email Notifications is checked, and in the users’ profiles, “For any event on all my projects” is selected for the notification setting.

Does anyone know of anything else I might be missing?