My wife read my emails, can I sue her?
"He who does not think himself worth saving from poverty and ignorance by his own efforts, will hardly be thought worth the efforts of anybody else." -- Frederick Douglass, Self-Made Men (1872)
While I don't see any sort of implied right to the privacy of the spouse due to marriage, I think the answer entirely depends on the nature of the relationship. My wife and I know all of each other's passwords and neither of us really care of the other checks their mail. In fact, I have had several conversations where one of us goes "the information you are looking for is in my email" with the full expectation that our email will be accessed by the spouse.
If my boyfriend reads my emails, then he has committed a crime in my book... I'd kick his *** for snooping and not trusting me.