Email Issue

System

I am using a workflow which sends an email with the attachment in HTML format when the job is complete.
I want my message to be always marked as "high importance". I have tried putting this in the header Importance => 2, or Importance => "High\r\n" in my email script but it does not work. I am using with MIME::Lite and remote SMTP relay server to send email. Does anyone know how to do this in perl using MIME::Lite. Please look at the attached file.