[d4mi3n]

Ownership of the email address/account is important. If you're using a corporate account, communicating on behalf of your employer, and have been informed ahead of time that all emails from said account are monitored, I don't believe many people could reasonably argue an expectation of privacy for personal correspondence in such a setting.

Additionally, if you work for a company or industry where such correspondence must be preserved and tendered on request due to applicable laws or regulations, such organizations are legally required to have access to all employee emails.