I like tools that are easy to install. This is one of them. It implements in your Gmail account via a small add-on.

The fact that this tool is free to use for your Gmailaccount. It is very simple to get into it, even for people with minimal knowledge about mailing statistics. You can see and analyze the data quick and easy.

I found Gmail Meter when I was searching for a way to optimise my inbox . It kinda works like Google Analytics - just working with data of your mail inbox only. I like that everything is automated and basically you just have to look at the report that will be send to you.