Can I mark an Email as “High Importance” for Outlook using System.Net.Mail?

Question

Part of the application I\'m working on for my client involves sending emails for events. Sometimes these are highly important. My client, and most of my client\'s clients,

Answer 1

Just because Outlook treats priority as importance, that doesn't mean all other email programs do so as well.

Priority and importance are NOT the same thing.

The correct answer is:

mail.Headers.Add("Importance", "High"); // High, normal, or low

values are case insensitive.

https://www.iana.org/assignments/message-headers/message-headers.xhtml
https://tools.ietf.org/html/rfc4021#page-32