Is it wrong to go through my boyfriend's email?

I went to check my yahoo email and he was still logged in. I found some emails where he had sent messages to women from the personals asking them to be his friend and also sent them pictures. He is always talking about how he hates cheaters and liars, so I would never expect this from him but once I got to an email from his sister's friend that was just the icing on the cake. She had sent him a very xxx video of herself in the shower. Should I confront him or was it wrong for me to even go through and should I leave it alone?