First, you need to edit Notification settings to make sure that you'll be notified about important events.
Then, you need to edit Email reminders to configure when emails will be sent to you.
Click on your photo (top right corner of the page) and select My account.
From here, click on Notification settings (left menu).
Make sure to select at least the following checkboxes. Then check the checkboxes below, towards the end of the page, and feel free to tick some of them if you wish.
Now, on the left menu, click on Email reminders.
We recommend to receive emails immediately when you are mentioned (@YourName appears in a comment), while other events can be collected in digests and be sent twice a day. So, this is the configuration we recommend:
Scroll down just a bit, and select your working days. So you won't receive emails from OpenProject when you're not working. As you probably noticed, you can also disable emails temporarily when you are on holiday.
Finally, in the last section, we recommend to tick all the checkboxes: