attachment is winmail.dat

One day when I login to my e-mail via mail client, found out attachment from new e-mail turn out become winmail.dat, where this never happen before, it try login to my web UI, check the attachment, it show the same type of file winmail.dat. I start wonder what happen to my e-mail account, I try clear up old e-mail, so that my mail server have more space available for new e-mail and attachment;

attachment as winmail.dat

I ask few friends sent e-mail with attachment from different e-mail provider, found out some attachment show it original type file, only attachment sent from Microsoft Outlook have problem, 

I wrote an e-mail to my mail server provider, they checked and feedback that: root cause is not from mail server, but from Outlook itself. 

http://email.about.com/od/outlooktips/qt/Prevent_Winmail_dat_Attachments_from_Being_Sent_in_Outlook.htm

Attachment sent out from one of the company e-mail, compose using Outlook, sent thru exchange server will turn into winmail.dat format. I ask the person change Outlook setting according the web link above, result still the same, attachment receive as winmail.dat.

Then he bring this issue to his company I.T. admin, and the result is: my e-mail address is set under their global address book in exchange server, and MAPI send e-mail using rich text!

contact in exchange server

To solve this issue, I.T. Admin remove my e-mail address in their global address book, and i resume receive attachment as original file type from that company e-mail again.

contact writer: Ngai Siew Kuen
e-mail:s_k_ngai 
Subject:[From Blog] attachment is winmail.dat