I can not get thunderbird 60 to open any attachments even in safe mode
When I try to open an attachment of any type, it asks me for the program to open it with. I have chosen thunderbird, firefox, windows media viewer and other add on downloads from your own lists. All are no good. This all happened after your most recent update.
Alla svar (1)
What kind of file is the attachment, and with which application shall the attachment be opened?
I have chosen thunderbird, firefox, windows media viewer
When Thunderbird can't open a given attachment, why would you even try to open that attachment with Thunderbird?
... and other add on downloads from your own lists.
What downloads and what lists are you talking about?
This all happened after your most recent update.
What update are you talking about?
See if this article helps. http://kb.mozillazine.org/Actions_for_attachment_file_types