By default, when you create an account on Discourse, you are set to receive summary e-mails every week and notification e-mails when someone replies to you. You can edit these settings in your personal preferences and fine-tune what kind of e-mail you want to receive. You can also apply different tracking levels to different categories (for instance watch all new posts and replies, or only new posts, or nothing).
On the other hand, if you like mailing lists, Discourse has a mailing list mode, where you receive an e-mail for every new post or reply. It apparently obeys muting: you may mute topics or entire categories.
If you want to share additional advice or ask questions on fine-tuning e-mails / notifications, please do it here.