If a corporation is a "person" before the law, then if the corporate person commits a crime, do you send the whole corporation to jail? I don't think so. While I'll grant you that the law's insistence on personhood forces the fiction that you have to treat a corporation as a person for the purposes of commercial contracts and to enter into binding agreements, this should not apply to criminal activities nor to criminal sanctions.

Personal responsibility is, for me, at the core of any system of justice, and a corporate entity BY DEFINITION can not accept personal responsibility.

Microsoft didn't create or dispose of incriminating e-mails. Individuals generated them and allegedgly disposed of them. I'm guessing that Microsoft has a security and privacy policy in place telling all employees that the use of the company e-mail system must follow guidelines and that it is not a personal communications device, thus obviating any expectation of privacy. That makes those communications reasonable targets for discovery, without extraordinary concerns.

Microsoft does have a right to protect itself from unreasonable disclosure of intellectual property or proprietary materials, but that is why the courts can seal records or appoint special masters.

Be careful about the road you follow with shielding individuals from scrutiny based on their corporate relationships. One fork down that road leads to, "I was just following orders" and we don't want to go there.