Pesky winmail.dat Issue

I have one client that uses Outlook and whenever she sends me an email with an attachment (or attachments), it comes as a winmail.dat (Transport Neutral Encapsulation Format) file that I have to open using a third-party app (TNEF's Enough).

I have over had many, many clients over the years who use Outlook and this is the only one with which I have this issue.

Conversely, she sends emails to users all over the world who use both Windows and MacOS, and I am the only recipient that has reported this issue.

I have researched the problem and found several explanations that attribute the issue to Rich Text Format settings in Outlook, but that has been explored and ruled out. Since this is a client with their own managed IT department, there's a limit to what I can request from their end, but I have been assured that this an edge case as far as they are concerned.

This happens on both the desktop and iOS versions of Apple Mail (attached):

It does not happen with the browser or IOS version of Gmail (also attached):

That tells me that it is indeed not an issue on the client's side.

This issue has come up several times before in this forum (winmail.dat - any way to fix this issue f… - Apple Community) and there never seems to be any resolution other than instructions on how to use a third party app to open the attachment.

Can someone please help me get to the bottom of this?

Thanks in advance.