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, use Outlook, which has the ability to mark a mail message as High Importance.

Now, I know it is callous to assume that all end users will be using the same interface, sp I am not. But considering you can send email from Outlook as High Importance even if the target is not necessarily reading through Outlook, that means that there is basically some data stored... somehow... that lets Outlook know if a particular message was assigned as High Importance. That's my interpretation, at least.

The application currently uses System.Net.Mail to send out emails, using System.Net.Mail.MailMessages for writing them and System.Net.Mail.SmtpClient to send them. Is it possible to set this "High Importance" setting with System.Net.Mail's abilities? If not, is there any assembly available which can configure this setting?