This category is for people who want to interact with Discourse by email. There are many reasons to use email, one of them is accessibility, another one is convenience and offline support.
Because it becomes quickly tedious to have an email address for each category, send your emails to email@example.com and the moderator staff will classify them for you.
For existing threads, configure Discourse to act more like a mailing list. Go to https://discourse.nixos.org/u/USER/preferences/emails , where USER is your account name and “Enable mailing list mode”.
For a discussion around the subject, see Discourse via Email