This is often due to an Outlook configuration or the "Rich Text" format.
Solution 1: Change the Outlook settings
Follow these instructions to change the settings for rich text mails:
https://www.lifewire.com/prevent-sending-winmail-dat-attachments-1173717
https://appuals.com/fix-outlook-sending-winmail-dat-attachments/
Solution 2: Change the format of the forwarded attachment
SoSafe can change the format from the EML file to three separate files:
- header
- Body
- Annexes
Please contact us directly and we will change the format for you.