A list's header filter rules got lost
I'm not sure when this occurred, but around 20 June 2016 I added a header filter at https://lists.mailman3.org/mailman3/lists/mailman-users.mailman3.org/header-matches/ for the subject
header with pattern =\?koi8-r\?
. After multiple updates to the underlying mailman core, this rule disappeared. I have just restored it.
It is possible that it was inadvertently deleted through Postorius, but I don't think so.