Can't fix my Send To Email client

A couple weeks ago, something changed in my Adobe Acrobat Pro, that I subscribe to with my University address (geplerwo@uvm.edu).  I used to be able to Send by Email using my default email client (Thunderbird); however, now it doesn't show up, and rather it tells me I have to create a Microsoft Outlook account.  I've never had Outlook, and when I try to ADD my Thunderbird email client (with greg@burlingtontelecom.net as my all the proper in and out servers), it doesn't "take" and it keeps telling me I have to create the Outlook account. 

Even though Send by Email had been working using my geplerwo@uvm.edu account for quite some time (this is my Adobe CC account), my email client is greg@burlingtontelecom.net, to which my UVM.edu emails are re-directed.  Does this have something to do with it?