Lars wrote:

Is there any update of any progress of a bugfix already?

Nope, not yet.

I have the exact same problem.
Looks like it has something to do with 'undisclosed-recipients'.
I don't know why, but even if I have one address as 'to' and two
added in 'cc' Outlook changes it into 'undisclosed-recipients' and
the problem seems to occur.

it has to do with receiving the message via Bcc. I don't think what's in
the To field has any bearing on it.

I can post the headers if needed.

No need.
--
Brian Tillman [MVP-Outlook]