From a legal point of view, can the contents of e-mails be used as evidence in court? What about QQ, SMS and other chat records?

Everything you say can be used as evidence, but we should examine the "three characteristics" of evidence, that is, objective authenticity, legitimacy and relevance. What you are talking about is "electronic evidence": specifically, judging whether an electronic evidence should be allowed to be adopted mainly depends on whether it is related to the facts to be proved, whether it is true in form, and whether there are major illegal acts in the process of its generation and acquisition; Judging the probative force of accepted electronic evidence mainly depends on its substantial reliability and relevance to the facts to be proved. Admittedly, the above measures are not equally important. In view of the fact that the computer system on which electronic evidence depends is easy to be attacked, tampered with and difficult to be found, and the electronic evidence itself is easy to be modified and difficult to leave traces, it is undoubtedly of special significance to examine the authenticity of such evidence. The civil procedure law stipulates that all evidence must be verified before it can become the basis for ascertaining facts; The Administrative Procedure Law stipulates that all evidence must be verified by the court before it can become the basis for deciding a case. These regulations show that any evidence has its fragility, so it needs to be "verified". According to this logic, as long as electronic evidence is verified, it can become litigation evidence like other evidence.