PHP Mail question

Hello,

In the majority of email clients you can select whether an email should flag as important. Usually puts a red exclamation mark next to the subject or where ever it is.

I'm wondering if it is possible to make this happen when a user selects it on a simple mail form.

I have a field called 'urgent', and the user can select yes or no.

So basically what I want is this;

if urgent is yes, make this email important.

I can't seem to find anything related to it, maybe it is an extra $headers line as well.

Can anyone help please?