Changing importance/priority for emails

[eluser]Unknown[/eluser]
Hi guys,

I haven't found an answer to this anywhere yet, but if it has been covered then apologies.

Is there a way to change the importance (high/normal/low) of a message being sent out using the Email class in CI version 2.0.2? Or would I have to write a header string to get around it somehow?

Thanks in advance