I have used this plugin for years and FINALLY figured out how to reply to messages that come in through my email. 

For anyone else that has experienced this and has been scratching their head, you need to put two variables in the Admin Email Message Options section FROM: email address

 {Your Name} {Email}

This will give you the name of the sender and give you the ability to reply to the form they submitted.

If you already know this, sorry.

Another Tip:  To make my emails come in clean, I also type in the name of my website and then put my email address in carrots:

Website Name (or any name of your choosing) <info@mydomain.com>

Ta dah