To minimise emails from Discourse (what I do myself):
First, you need a way to make sure you get notifications (especially Personal Messages) that is workable for you. While you can enable notifications in your browser if you use your PC for this, many find the mobile app more helpful:
Second, change the Email settings (under Settings / Preferences / Emails) to halt the emails; you may wish to keep them for messages. At the same time, I suggest that you turn on the Activity Summary with a frequency that works for you. This can also act as an alternative way to be notified of messages (albeit with a delay):
