Finally he unsubscribed and re-subscribed. If I recall, that seemed to fix things.
Does not work for me though. I cannot unsubscribe through the web interface - I follow all the steps and apparently an email is supposedly sent to me, though that never arrives in my mailbox.
That's strange because I receive lot's of email through the mailing lists I am (definitely still) subscribed to.
I know from f2f Perl Monger Meetings, that there is at least one more such kill file like victim.
(hooked on the Perl Programming language)