Thanks for your posts on this Gene.
I will include this instruction for updating thew hosts file.
It's a little trickier in Windows 10 than it was in previous versions.
https://www.petri.com/easily-edit-hosts-file-windows-10The hosts file tells your computer that you are hosting a domain name.
I added the line "127.0.0.1 platform.twitter.com"
Administrator rights have to be used to resave the updated file. The file is saved without a suffix.
The result:
When Thunderbird tries to access the web to open an image requested by the script, it stops at my computer and can't find it. The request never goes to Twitter. The browser isn't opened to view the image and I'm able to look at the messages like normal. If Twitter ever uses this domain for any critical functionality, it could break the ability to use Twitter. Right now, Twitter is working fine for me.