/var/lib/qmail/queue/mess/ is in qmail 1.06-5.
This file is owned by qmailq:qmail, with mode 0o750.
..
/var/lib/qmail/queue/mess/0/
/var/lib/qmail/queue/mess/1/
/var/lib/qmail/queue/mess/10/
/var/lib/qmail/queue/mess/11/
/var/lib/qmail/queue/mess/12/
/var/lib/qmail/queue/mess/13/
/var/lib/qmail/queue/mess/14/
/var/lib/qmail/queue/mess/15/
/var/lib/qmail/queue/mess/16/
/var/lib/qmail/queue/mess/17/
/var/lib/qmail/queue/mess/18/
/var/lib/qmail/queue/mess/19/
/var/lib/qmail/queue/mess/2/
/var/lib/qmail/queue/mess/20/
/var/lib/qmail/queue/mess/21/
/var/lib/qmail/queue/mess/22/
/var/lib/qmail/queue/mess/3/
/var/lib/qmail/queue/mess/4/
/var/lib/qmail/queue/mess/5/
/var/lib/qmail/queue/mess/6/
/var/lib/qmail/queue/mess/7/
/var/lib/qmail/queue/mess/8/
/var/lib/qmail/queue/mess/9/