Or better yet, jailbreak your kindle before the hole is closed, install koreader, and read epub natively. It's a much better reader compared to the built-in one anyway.
And you can send straight to the Kindle from Calibre via WiFi, no need for /sendtokindle.
Thanks for the useful link!
I guess I am being overly paranoid, but I always also add a virus total check on top of it to make sure the file is clean [1]
[1] https://www.virustotal.com/gui/home/upload
/sendtokindle seems a bit brave if you obtained your epub off the back of a lorry..
KOReader + Calibre is also fully wireless. Get a Kobo, not a Swindle.