otrs.PostMasterMailbox.pl exit status 1 on cron

[mjavahery]

Hi
When I run otrs.PostMasterMailbox.pl manually, it works fine and all emails from external accounts (12 Exchange accounts) are retrieved and processed. However, when it is run by cron (either from OTRS config files or crontab, even if path is given explicitly), messages like these appear in syslog and no email is retrieved:

Jan 21 08:43:01 localhost /USR/SBIN/CRON[13795]: (otrs) CMD (/opt/otrs/bin/otrs.PostMasterMailbox.pl >> /dev/null)
Jan 21 08:43:02 localhost /USR/SBIN/CRON[13794]: (CRON) error (grandchild #13795 failed with exit status 1)

Please help,
Thanks in advance.