Outlook sending attachments as "winmail.dat"

If you are having trouble with some contacts not being able to open your attachments, and you are sending to them from Microsoft Outlook, this tip might help.

Outlook has some elements that are tied to sent emails which can't be properly read by certain other email programs or devices on the recipient side.  This may result in your email that had an attachment being received with a random winmail.dat file on the other end.

To resolve this issue, try these steps:

Option 1

1. In the compose window, click the "Format Text" ribbon.

2. Near the left, under the "Format" section, change from "HTML" or "Rich Text" to be "Plain Text".  This will cause you to lose any pictures in the body of the email as well as any "fancy text", but might help the receiving end to properly receive your attachment.

If this doesn't work, try this:

Option 2

1. Check if the contact is stored in your contacts.  If so, manually record any important contact information.

2. Delete the contact from your list of contacts.

3. Find an email coming from, or going to this same contact and open it.

4. Right click on their email address and click "Open Outlook Properties".

5. On the "Internet Format" drop down, choose "Send Plain Text only" and click ok.

This will force your emails to be sent to this contact as Plain Text.  You should now also be able to re-add them to your contacts.  You can right click the email address and click "Add to Outlook Contacts".

Option 3

If you have Outlook 2013 or 2016, you may be having a hard time getting the "Outlook Properties" window with the "Internet Format" drop down to even show up.  This might require you do add a registry entry.  We strongly suggest that you only proceed with these steps below if you are 100% comfortable.  Changing 1 incorrect entry in the registry can render your computer useless.  We are able to perform these steps for you with a remote session if needed.

1. Close Outlook.

2. Press Windows Key + R in Windows.

3. Type "regedit" under Open: in the Run dialog.

4. Click OK.

5. If you get a User Account Control popup, click Yes.

6. For Outlook 2016, navigate to: HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\Contactcard (if you don't see this last folder, see step 8.)

7. For Outlook 2013, navigate to: HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Common\Contactcard (if you don't see this last folder, see step 8.)

8. If you don't see the Contactcard folder, keep the Common folder highlighted, then click Edit, New and then Key - name the folder Contactcard and press enter.

9. With the Contactcard folder highlighted, click Edit, New, DWORD (32-bit) Value and name it "turnonlegacydialog" in the Name column, then press Enter.

10. Double click the newly created "turnonlegacydialog" value.

11. Change the Value data from 0 to 1 and click OK.

12. Close the Registry Editor.

You should now have the "Outlook Properties" window referred to in Option 2.

CompuSave Computers Inc. is more than happy to assist you with your email setup. We do however charge for services rendered remotely, on-site and in-store.

CompuSave Computers Inc.

Your Technical Team - On Your Side

Call or Text: 519-863-6336  -  Email: support@compusave.ca

Website: www.CompuSave.ca

Posted: December 2018, Updated January 2019

Author: BK