He shouldn't have been going through his wife's e-mail, but in my opinion this should be more of a moral problem than a criminal problem. In other words, he was in the wrong, but he shouldn't go to jail or go to court over something so stupid.
In this case, I don't think so because it was a shared computer and they were living together and it doesn't sound like he hacked into her account. I think it might be a little greyer area if he had hacked into her account or computer in order to gain access.
It is wrong for reading someone else's email. I do not agree with this, but I do think that the punishment is very severe. It to me is more of a moral issue.