For some reason the mail log was showing lots of:
Sep 23 09:40:03 hostname qmail: 1253695203.637058 alert: cannot start: unable to open mutex
Sep 23 10:32:16 hostname qmail: 1253698336.515510 alert: cannot start: unable to open mutex
Sep 23 10:32:21 hostname qmail: 1253698341.425333 alert: cannot start: unable to open mutex
and qmail was not working properly.
It turns out that for some reason /var/qmail/queue/lock/ was missing along with the file /var/qmail/queue/lock/sendmutex. Had to recreate these with:
[root@hostname ~]# mkdir /var/qmail/queue/lock/
[root@hostname ~]# chown qmailq:qmail /var/qmail/queue/lock/
[root@hostname ~]# touch /var/qmail/queue/lock/sendmutex
[root@hostname ~]# chown qmails:qmail /var/qmail/queue/lock/sendmutex
Then qmail would start fine.
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