I was trying to send Python documentation that is available as an epub file here:
https://docs.python.org/3/download.html
The file is not large (~7 MB) but very complex (many internal links and files).
I tried to send it via Send To Kindle (web or PC) and for several minutes I got a "Processing" message and finally "Failed. Please retry".
I also tried using Calibre to simplify the structure of this file, but to no avail.
Does anyone have an idea?