Syed Jahanzaib Personal Blog to Share Knowledge !

June 8, 2012

winmail.dat issue in Lotus Notes [Solved]

Filed under: IBM Related — Tags: , , , , — Syed Jahanzaib / Pinochio~:) @ 10:00 AM

Howto Solve the winmail.dat issue in Lotus Notes

We are using IBM Lotus Domino Mail Server ver 8.5.3 / FP6.

From past few days, Some of our Lotus Notes Users were getting “winmail.dat” in attachments  & they were unable to open it . After some research it revealed that the the sender is usually from Mircosoft Exchange/Outlook User.

After some googling, I was able to sort it out.


Open Lotus Domino Administrator ,

  • Goto SERVER

& issue the following commands , Paste following two commands , one at a time . . .

  • set config TNEFKeepAttachment=1
  • tell router update config

The problem is that Outlook is tunneling rich text formatted information in an attachment through the Internet using a proprietary format (by Microsoft), rather than MIME (an Internet standard).

Microsoft opened up the format so other vendors could read the content, and IBM and other vendors have included that ability in later patches.

For more info, please read the below article from IBM.

Syed Jahanzaib


  1. Hi Syed,

    Can you email me about some freelance work? I have a small project that involves setting up an RB750 to work as a hotspot, but I want users who are NOT authenticated to go through an external proxy (squid or something) where I can control what they see via the external proxy, and I want authenticated users to bypass the external proxy and have direct access to the internet.



    Comment by John Klein — June 8, 2012 @ 9:37 PM

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