I have actually argued for the use of mailing lists for corporate engineering discussions. When that becomes the medium for code review or design discussions, there's a nice streamlined workflow. Further, it's practically trivial to write or customize a mailing list reflector. If you have a decent and secure mail client library, you're a weekend away from it just working. Contrast that with customizing or rolling your own IRC, Slack, Discord, or web forum clone. Mailing lists don't suffer from vendor lock-in, and anyone with a mail client and who can follow basic rules can participate.

An invitation-only mailing list with a reflector that verifies PGP encryption and non-repudiation is just fine for most corporate discussions. For mailing lists open to the public, new users can be placed in a moderation queue for a period of time until it's clear that they understand list netiquette and formatting rules.