Getting "Recieved:" headers from rfc822 Message objects?

[Gustaf Liljegren]

Python 2.1, regarding the rfc822 module:

I have found some mails in my inbox that have no "Date" header. So instead, 
I though about using the date in the last recieved header of a Message 
object. How do you recieve the "Recieved: " headers? I have tried 
m.getallmatchingheaders('recieved'), but it returns an empty list.

Regards,

Gustaf Liljegren