How to enable 'Mailing list mode':
Click the user icon at the top right of the page, click the user tab, click Preferences, select Emails, then tick 'Mailing list mode'. You can choose a daily digest, or individual emails.
It seems to me that Racket Discourse doesn't have the option for starting new topics via email enabled. When I tried just sending an email, I got a reply with "[Racket Discussions] Email issue -- Unknown To: Address" subject.
Hmm... well, I just spent five minutes searching, and I can't find the relevant setting, if in fact it exists. Let me know if you can find anything on meta.discourse.group
Okay, yay! Found it.
Down side: there are some things to configure, and some gotchas.
One fundamental issue is that by default, users must be at trust level 2, "member", in order to start new topics. Thinking harder, this is probably a foundational pillar of spam prevention, and I'd be leery about adjusting that.
Second, it looks like there's some configuration work to do around choosing email addresses and even a possible authentication server, ugh.
It's not yet clear to me whether this is required or simply available.