Simply run these commands. You will be ok in no time 🙂
These commands simply delete all email files from all sub-directories of qmail queue root directory.
It works like a charm for current version of kloxo.
qmailctl stop
find /var/qmail/queue/mess -type f -exec rm {} \;
find /var/qmail/queue/info -type f -exec rm {} \;
find /var/qmail/queue/local -type f -exec rm {} \;
find /var/qmail/queue/intd -type f -exec rm {} \;
find /var/qmail/queue/todo -type f -exec rm {} \;
find /var/qmail/queue/remote -type f -exec rm {} \;
qmailctl start
Hope it helps!