[otrs] No Sent Date and Time in OTRS Emails and notification

Hi, I see "Sent: None" in email (Ms Outlook 2003) replies/notifications sent by OTRS (1.3.2) running on RHEL 3 AS, I have tried sending this email from my two different email servers (qmail and VPOP) but both have the same results. I am sure there is some thing wrong with OTRS, email servers are working perfectly. Please help. Asim