Microsoft Outlook is the favorite email client of majority of the corporate businesses. The businesses do not need to purchase it separately as it is available with MS Office Suite and nowadays with Microsoft 365 subscription. Some of the users who are working with other email client may get the Winmail.dat issue related to the attachments.

Outlook uses Rich Text Format that consists of many features, one of which is text enhancement. So, when a non-Outlook user receives an RTF email, then he also receives a Winmail.dat attachment. This Winmail.dat attachment is a file that contains all the information of such text enhancements.

Why does the Winmail.dat attachment issue arise?

Outlook is a Microsoft product and that’s why it has some features which are specially supported by Microsoft applications. But not every time this exchange of emails happens between Outlook users. Sometimes, Outlook users send these emails to non-Outlook users which leads to this situation. Outlook uses Rich Text Format to send the emails and attachments which is only supported by MS Exchange, Gmail and Outlook and hence any other recipient may face this issue.

How to Fix Winmail.dat Attachments

It’s not a problem that requires a solution, but it is a kind of issue that needs a few changes in the settings. So, let’s know what measures should be taken in order to make it right.

  • Changing the email format

    Yes, changing the email format will provide you guaranteed results if the problem was arising due to it. This problem is arising due to the format unavailability issues in most of the cases. So, you can try to change the email format in two ways:

    1. Changing the email format while sending the email

      If there are just one or two people facing this issue, then you can change the email format every time you compose an email for them. For this, you need to compose an email just like you do, but before sending it, click on Format and then select Plain Text as the final format. Once done, send the email.

    2. Changing the default email format

      If the first method seems quite hectic to you and you do not want to change the format of the email every time you send it. Or if the number of the receivers are more and it is a frequent affair, then you can change the default email format. By doing this, every time you send an email, it will be sent in Plain Text Format. Follow the below-mentioned steps for the same:

      1. Open Outlook and click on the File tab on the top.
      2. Now in the File’s menu, select Options category.
      3. As the Options Window pops up, go to the Mail category.
      4. In the Mail category, locate Compose messages in this format, and in the drop-down beside it select Plain Text as the default email format.

      After applying all the changes mentioned above, all your emails after this will be sent in Plain Text format automatically. This will fix the issue forever, if it doesn’t maybe you can apply the next method.

  • Prohibit selected users from receiving Winmail.dat attachments

    In this method, we will talk about keeping some of the selected users from receiving the Winmail.dat attachment. So, let’s not stretch it more and discuss how to prevent some of your contacts from receiving the Winmail.dat.

    1. Open Outlook and verify that the recipient(s) should not be in your contact book.
    2. Now compose an email and in the To section enter the recipient’s email address.
    3. Make a right click on the email address you have entered and select Open Outlook Properties from the options.
    4. An E-mail Properties dialogue box will pop-up, there from the Internet format drop-down box select Send Plain Text.
  • Modify Registry Editor settings

    Here we are going to discuss another way to prevent the recipient from receiving Winmail.dat attachments. We are going to do it through the Registry Editor. As this method is a bit complicated and can also bring some unwanted complications, we do not recommend using it unless it is too important. Or we suggest you to do it under the guidance of a knowledgeable person. Before starting the process, make sure that the Outlook and all of its instances are closed in your system. Now, let’s check-out the process:

    1. Press Win + R key to open the Run Window.
    2. In the Run window, type regedit and click on OK.
    3. Once done, navigate this path for Outlook 2016:
      HKEY_CURRENT_USER \ Software \ Microsoft \ Office \ 16.0 \ Outlook \ Preferences
    4. Once the Registry Editor is open, locate Preferences and make a right click.
    5. From the options list select New and then DWORD (32-BIT) Value.
    6. Now, name the DWORD as DisableTNEF and change the Value data to 1.

Once done, close it all and see if the problem is now solved. So, this was all about the Winmail attachments issues users were complaining about. Any of the above-mentioned methods should work for you, or check this if you are unable to open Outlook attachments. If there is any other issue in Outlook which you are suspicious of like a corrupt PST or you want to convert or migrate a PST, we recommend you Outlook PST Recovery to fix any sort of corruption in a PST file.

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Outlook PST Repair software will help you in recovering the attachments of your emails separately from your emails. After that you can restore them in a new PST file and get rid of winmail.dat problem completely.