Pywin32 generated msg with html content opens in outlook as plain text

[encleadus]

Expected behavior and actual behavior.

I had a working code which generates with predefined html content msg files based on a list. Then our operator clicking on the msg files and manually add the recipients and send the email. This was working I guess, until an office update happened in last December or this year January. The current behavior is that opening the generated msg file will open as plain text.

I read similar issues on the Microsofts forum page:

link1

link2

However these looks like have been fixed as if I manually save email to msg file and reopen it, outlook will opens it in html view.
I can only think something changed in outlook msg export/save which is not introduced in pywin32.

Version of Python (3.12.2) and pywin32 (306)