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Outlook can sometimes reformat attachments to 'winmail.dat'. This is most often when the email client is sending out emails that contain Rich Text such as bolg, italics, etc. The formatting is stored in the winmail.dat file. The recipient email clients may store that data as an attachment. Other normal file attachments are also stored as winmail.dat files as well. Below is a quick guide on how to stop this from happening.

How to prevent winmail.dat file types in Outlook

  1. Open up your Outlook email client.
  2. Click on File located in the upper toolbar.
  3. Select the Options setting.
  4. From here, select the Mail category.
  5. Now, under Compose messages, you want to ensure the HTML or Plain Text option is selected for the Compose messages in this format.
  6. Next, underMessage format, set When sending messages in Rich text format to Internet recipients to Convert to HTML format or Plain Test format
  7. Click OK to finish.

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n/a Points
2015-05-23 4:54 am



I am Idrees working in a buying office and do communication with my different buyers.

I am using Microsoft Outlook for communication with buyers. I am facing some problem with my email account as i am getting email attachments with winmail.dat.txt instead of regular pdf files. My other coleagues receiving the same email with pdf attachment, while i am getting the email with winmail.dat.txt attachment. 

Please confirm the method how I can resolve this issue. Due to this issue I can't be able to get actual attachments those are my buyer sending in pdf format.




10,077 Points
2015-05-27 12:19 am
Hello Idrees,

Has your buyers followed the steps to prevent outlook from converting the file to a winmail.dat file? Even if you make these changes they would have to as well.

Best Regards,
TJ Edens
n/a Points
2015-06-13 9:23 am

The instructions do not apply to me and wouldn't work.

I already have my emails sent in HTML and the convert box in step 6 was already checked.

The problem happens anyway.

However, if I send the email in text mode, the PDF file is not converted to a dat file.

Text mode appears to be the only workaround. → too bad Bill Gates doesn't use some of his billions to fix stuff like this.

n/a Points
2015-11-03 12:28 pm

You realize Bill Gates doesn't run MS anymore, right? I'm just going to give you the benefit of the doubt here. 

n/a Points
2016-07-21 8:12 am


how to remove winmail.dat from outlook 2013 

11,946 Points
2016-07-21 8:37 am
The resolution is described in this article from Microsoft:
n/a Points
2016-11-14 1:59 pm


Does not work for Outlook 2016. Cheers Microsft, bunch of w****s. Only works with new email addresses.


About time Microsoft put an option in Outlook "Send winmail.dat Yes/No!!!!"

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