Mailing lists aren't federated. Everyone has to email one particular address at one particular domain; whoever controls that email address + domain can censor/block emails. (That's a good thing when you're blocking spam!)
If you're OK with the fact that mailing lists are somewhat centralized, there are actually got a ton of great alternatives to pure mailing lists.
All popular open-source web forums support email notifications, and most of them support posting by email, (I know phpBB and Discourse do,) and all of them have sitemaps with crawlable archives.
If you're OK with the fact that mailing lists are somewhat centralized, there are actually got a ton of great alternatives to pure mailing lists.
All popular open-source web forums support email notifications, and most of them support posting by email, (I know phpBB and Discourse do,) and all of them have sitemaps with crawlable archives.