Not sure why this does not exist today but I did not find a way to do it or reference to it here in the Thwack community.
Within Outlook we have the ability to mark the importance of an email we are sending with "High Importance" or "Low Importance" as opposed to "Normal Importance". When the email is received, a red exclamation mark symbol for High or blue down arrow symbol for low appears in the email list for that email. This can help the receiver to prioritize their email review.
Here we send out Critical (production level device/app issue), Warning (non-production level device/app issue) and Informational (backup successful, etc.) Alert notifications via email. It would be very helpful if we could send that with the importance flag attached.