I usually download ebooks from Anna’s Archive and transfer it to my Kindle through the service. But 1/10 times it fails, with no apparent reason. The particular ebook in question is https://annas-archive.org/md5/e310a253a9d85992129cc2b8dd351556. What’s the way out?
Kindle supports epub now, and if you try to send a mobi formated book through email to your kindle, then Amazon will send you an email telling you that that format has been depreciated.