@Terrificli -- I am not sure whether an ISP can inspect your email or even if there is a way for anyone to find out if your ISP is looking at your email. After all, you are using their servers and one should assume that an ISP would have access to all information moving along its network.
But I wouldn't worry about it. Back around 1999, I visited with the owner of a small, local ISP and asked him if his company kept up with what people were doing online. He said that was almost impossible because so much information was flowing that keeping track of it all was well night impossible. That was 15 years ago when the Internet was a much smaller place. How much harder is it for an ISP to keep tabs on its customers today?