Acrobat 9 Pro (Version 9.5.5) "attatch to email"

Hey,

I'm having Acrobat 9 Pro (Version 9.5.5) on Windows 10 (build 1909) with Office 365 (Outlook). This is the setup of numerous PCs. The "attatch to email"-feature works quite well, except on one of the PCs 😞

The error is that there is no Stadard Email-Application set. - which of course - wrong.

Sending attachments from the OS and from Acrobat Reader  is working fine.

The "attach to email"-feature of the Acrobat Pro is used a lot and so I'm looking for a fix. I did try a lot of things mentioned in the knowledge base and on other websites. E.g.:

- Reinstall and fix Office installation (same with Acrobat)

- Reset Standrad-Mailprogramm

- Execute fixes mentioned in the knowledge base

- Check and set keys in the registry

...

Unfortunatelly most solutions had Windows 7 or so. Maybe therefore I wasn't able to fix the problem. Can anyone provide me with tipps or an solution?

Big thanks in advance