I just updated to Thunderbird 91.2.0 and now, every time Thunderbird starts, I get an error message "Either there is no mail client or the current client cannot fulfill the messaging request. Please run Microsoft Outlook and set it as the default mail client." (See attached) Huh? I have Outlook installed on the machine but have never used it. Also, after I click off on the error message (two times), all of my folders appear expanded. I did a System Restore to last week but then I couldn't open either Thunderbird or Firefox because the recent updates changed the profile structure, so had to use Opera to download both and then update. Anyone else have this problem? Thanks in advance.