LOR's format

I know a couple of my LOR's (which I work for) are not the handiest at computers. Should they have a signature on their letter. I don't think this has happened. One of my science LOR's is used to this type of request so I'm sure his letter is fine. My other science LOR no longer works at the institution but knows me very well to give me a proper recommendation.

If there is a glitch with one of the letters in a specific requirement etc will the school contact me?