Running Outlook 2007, Vista Business Edition.

My domain is being spoofed by a spammer. I know this because I am receiving
dozens of "mail not delivered" bounces containing the original message as an
attachment (it is an advert for Viagara.) The original message is from a
fake sender name @ my domain.

How do I view the Internet headers of the original message attached to the
bounce mail? I have saved the message and edited it but the header appears
to be encoded and is unreadable.

TIA
Andrew

PS: Reading the headers used to be easy - why is it now so difficult?