That’s a 6.5 year old page last updated 3.5 years ago; there’s been a bunch of threads since then essentially about replacing mailing list mode, eg Apply "mailing list mode" per category - feature - Discourse Meta with the result that mailing list mode was disabled by default in 2021. Current docs are here and apparently this is the generic link to your email preferences.
(Note also that email notifications are delayed by a few minutes so that if a topic is edited immediately after posting, you get the edited version in email)