I'm using Sendy to send ~15k emails every day. It works fine with a few hiccups. It stops sending after every few hundred and I have to keep hitting the 'send' button again. I've scripted this so it automatically happens. I'll admit I'm due for an upgrade which may have fixed that bug, but I made some minor modifications to the Sendy code which I just don't want to try to port to an upgrade.

Know that Sendy does a phone home which is just to check if you actually purchased the code. There is also a obfuscated file that I've unwound if you were curious:

https://gist.github.com/tittietime/0284ce3b6ef5e4fd35d3aa105...