Solving the dreaded winmail.dat issue in Lotus Notes

Strongback Consulting

So your users are getting these “winmail.dat” attachments in Lotus Notes and can’t open them, nor can they see any special formatting that the sender had added (and the sender is ALWAYS from Outlook).

Quick solution:

  1. Make sure you are on the latest fix pack of Lotus Domino. That should be 6.5.6, 7.0.3, 8.0.2, or 8.5.x.
  2. Open Lotus Domino Administrator and issue the following commands (copy and paste one at a time):
Set config TNEFKeepAttachment=1

set config TNEFEnableConversion=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 (concocted by Microsoft), rather than MIME (an Internet standard). It (wrongly) assumes the recipient is also using Outlook.

Microsoft opened up the format so other vendors could read the content, and IBM and other vendors have included that ability in later patches. You should not have this problem at all on Domino 8.5x, but will have to issue these commands on older versions of the server.

This and several other little “gotchas” can be easily resolved if you know where to go. If your organization does not have a dedicated Domino admin, it may benefit from having someone come in and help on an ad-hoc basis. Just contact us for more info. If you need help upgrading we (Strongback Consulting) offer upgrade services on all platforms (System i, Unix, Windows, Linux).

Also, if you are not on the latest and greatest of Notes/Domino, there are some features you are missing out on. Mainly the newest social features built into the product. SlashdotMedia has a great article on how email is going more social and not just inbox-centric.

If you are still using a version of Lotus Notes/Domino earlier than version 8, you are about 5 years left in the dust on technology. The product has changed considerably in version 9 with the IBM Notes Social Edition.


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2 Responses to “Solving the dreaded winmail.dat issue in Lotus Notes

  • TNEFEnableConversion=1 is the proper command to turn on the conversion.

    TNFKeepAttachment=1 just tells the conversion to keep the winamil.dat attachment in addition to the proper attachments.

  • I have run into this and similar issues a number of times with/without attachments and sometimes other recommendations work re: plain text format. Always the person received a winmail.dat file. However, a couple times it didn't and I found another fix on the Outlook client end. Issue was to do with the cached addresses of previously sent emails. So I opened a new email and started typing the recipient's name. As it started to prompt for the address I then clicked the 'x' to delete the cached entry (2007/2010 and Ctrl+Del in <=2003) and manually re-typed the address and hit send. Voila, message received in entirety!

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