Originally mailing lists were @wikipedia.org and then moved to @wikimedia.org and maybe @mail.wikipedia.org at some point before ending up at the current domain of @lists.wikimedia.org. See the 2007 announcement.
We still support those domains for legacy lists: https://gerrit.wikimedia.org/g/operations/puppet/+/d15a397fe548d041c4aa3932a4a83f29e9d2fb68/modules/role/templates/exim/exim4.conf.mx.erb#261
Do we need to continue supporting those old domains?