Can't search mailing list archives

["Rebecca N. Palmer" <r palmer bham ac uk>]

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 
]----------
Google

404. That’s an error.

The requested URL /custom was not found on this server. That’s all we know.

-----------------

This happens in Ubuntu/Firefox both with and without JavaScript.  The 
similar-looking search boxes elsewhere on the GNOME site do work.  This 
is *not* bug 662706: I don't see the second search box it mentions at all.
It appears the problem may be that Google have moved their custom search 
to /cse, as that is the address I see when using it from another site 
(where it does work for me).
Workaround: Typing site:mail.gnome.org and the search terms into an 
ordinary Google search box gives a similarly restricted search.
Furthermore, the help pages https://mail.gnome.org/ and 
https://wiki.gnome.org/action/show/Sysadmin/MailingLists?action=show&redirect=MailingLists 
suggest reporting such problems to mailman gnome org, which doesn't work.