There is a strange problem with our installation - we get the daily mail report only once - the day after zimbra is started/restarted. The following days, there is no daily mail report.

On running the following command as zimbra:
/opt/zimbra/libexec/zmdailyreport -m


No errors or warnings are seen on the console but, there is an error entry in /var/log/zimbra.log:

zimbramon[4039]: 4039:err: 2007-08-14 11:51:55, zmdailyreport: Failed to email report: Died at /opt/zimbra/zimbramon/lib/Mail/Mailer.pm line 285.

Where should I start looking to fix this problem?