I don't think that you having email conversations with a male friend should be private. That would be a secret.

H has lots of female friends. I don't have nearly as many male friends. I don't want to get into a "can men and women be friends" convo but it does go back to that. As for his internet friends, I really don't know who they are since I don't talk to them. So I guess we both have secrets.
But doesn't it really come down to trust.
Sure, you and MrsNop have each others passwords but why is that really necessary if you have a strong healthy trusting R/M. Anyone can open a new account without the other person knowing. So you think you have all access but you really dont. My point is if people want to keep a secret they will. There is no way to force the issue of trust. It is either there or it isn't. In my case, it isn't.