Given the aggressive spam filtering with mail forwarding to Gmail accounts, a huge proportion of the email accounts in use, it is not practical for us to run the XEmacs mailing lists any more (manual moderation will not work with the level of spam these long-existing, long-publicized addresses received, and automated filtering with SpamAssassin will occasionally let spam through, something that endangers further mail delivery from the forwarding mail server).
The archives remain available at https://list-archive.xemacs.org/, and I encourage open discussion at comp.emacs.xemacs , also available as https://groups.google.com/g/comp.emacs.xemacs on Google Groups.