I have just resolved an issue that I thought someone else might run into in the future, so I'm posting it to the list for future googlers. Problem Symptoms: * OTRS cron jobs are not executing, as a result no remote e-mail fetching is occurring * Manually running "Fetch Mail" from the admin interface functions properly * Manually executing "su -s /bin/sh -c /opt/otrs/bin/otrs.PostMasterMailbox.pl otrs" as otrs user functions properly * Adding "opt/otrs/bin/otrs.PostMasterMailbox.pl >>/dev/null" executes properly. * /var/log/cron contains the following errors: o crond[6551]: Permission denied crond[6551]: CRON (otrs) ERROR: failed to open PAM security session: Success crond[6551]: CRON (otrs) ERROR: cannot set security context System: * CentOS 5.x/RedHat 5.x * OTRS RPM install * selinux permissive * crond is running Solution: The cron.log error indicates that the problem is located somewhere within the PAM stack, which is preventing crond from launching a shell owned by the otrs user. The system in question is using /etc/security/access.conf to limit login access to the server. (Useful for limiting login access when the system uses some form of centralized authentication.) Other required PAM modules may also interfere. In this case adding a line to permit the otrs user login access via cron: + : otrs : cron crond or less secure + : ALL : cron crond