I actually just switched to Thunderbird last year because I needed to post a patch to a mailing list and I couldn't find any mail apps for Windows that could do

I actually just switched to Thunderbird last year because I needed to post a patch to a mailing list and I couldn't find any mail apps for Windows that could do it properly. Previously I used Alpine, but that was a much worse experience because pasting didn't work so I had to clumsily read in a prepared file from disk and not touch any other keys after that for fear of it rewrapping everything. If there are any other mail apps that do this better, and can still connect to "modern" (read: annoying) oauth setups like Office365 etc, I'd definitely be interested in trying them. I don't hate Thunderbird, but to me it seems like the least bad option for supporting both modern top-quote style HTML email and oldskool 7 bit ASCII/triangle bracket quoting/inline patch style email.