If you going to zmail.miad.edu you're likely seeing a message similar to this one
You can add exception, or click on the advanced tab to allow you bypass this message and access your email like you did before.
The reason you're seeing this message is due to a certificate expiring. The connection is as secure as the day this certificate was not expired, and no information is being revealed.
If you have any questions or need help please contact us at email@example.com, stop by the desk or give us a call. This issue should be rectified by this morning and this page will be updated.