The search box on the top bar of mailing list/archive pages (eg. https://mail.gnome.org/archives/gedit-list/ ), which I assumed to be the mail archive search box as there is nothing else for this, fails with the following error:
--------[URL bar: https://www.google.com/custom?q=plugin&domains=mail.gnome.org&hq=inurl%3A%2Farchives%2F&sitesearch=mail.gnome.org ]----------
Furthermore, the help pages https://mail.gnome.org/ and https://wiki.gnome.org/action/show/Sysadmin/MailingLists?action="">MailingLists suggest reporting such problems to mailman gnome org, which doesn't work.