Setting Content-Type when sending e-mail

Hi chaps,

Another obscure request that I'm not sure is doable. I want to be able to set the content type of an e-mail sent, similar to what my BlackBerry does with it's meeting requests, it assigns the following:

Content-Type: text/calendar; name="meeting.ics"; method="REQUEST"

I'm using the DesktopOnly library to send out the e-mail currently.

Thanks in advance,
Rich