Mailscanner Problem with Microsoft Outlook ?

[Devi Sambamoorthy]

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I am using MailScanner  (4.29.5) )with ClamAV and SPAM Assassin. I am
having a problem for the past one month.
 
A mail sent from an user  Tim is not reaching other Tom. But Tim is
receiving mails from everyone else.  Also Tom is able to send mails to
everyone else.
1. They are the only users of Microsoft Outlook in my Organization
2. The mail log status says that the mail has been sent 
 
I have set
Expand TNEF = yes
Deliver Unparsable TNEF = no
Should I change these values ?
Anyhelp is greatly appreciated!
I am not having even any clue about this problem.
 
 
Thanks,
Devi S.