Invalid address: Message body empty

I see this error message was resolved due to gettest was not installed. I assume it is the same issue for me.

1. how do I check if it is installed.
2. what changed that gettest is required? I would never have upgraded if I knew a different function would be required. If gettest is needed to be installed then I am at the mercy of my hosting company to get it installed -or if they don't then I need to move my install to somewhere else.