I now have Thunderbird 91.3.0. Still, detached pdf or jpg files don't open - but other detached file types like *.doc or *.docx or *.xlsx do open (and also did in 91.2.x).

What is the difference between detached pdfs (or jpgs) and other documents ? (In the file type settings, I see no difference - all are set to Always ask).

I would really like to continue using Detach and still open documents without going to the folder.

The problem seems to be known also to others: https://bugzilla.mozilla.org/show_bug.cgi?id=1738490

Would be nice to solve it.

I would guess that the JPG and PDF file formats are handled internally in Thunderbird. But as the data is no longer in Thunderbird that does not work.

Try specifying an external program to handle those types of attachments in preferences.

That does not work. Specifying Adobe Acrobat Reader instead of "Always Ask" for pdf still does nothing. Specifying Preview in TB works, but I want the attachment to open in Adobe Acrobat Reader.

Since the problem is encountered also by others https://bugzilla.mozilla.org/show_bug.cgi?id=1738490 it would be nice to have it solved.

The bug is the canonical topic. Posting here gains nothing as any change will be discussed and recorded there. Not here. I even doubt if the head architect has looked in this forum ion the last 12 months.

OK, so I'll look there and hope for a solution. I hadn't been aware of that forum until some expert sent me the link.

But thanks for trying to help.