In Outlook Express: select the bounced message, right click on it and click on 'Properties". Select the'Details' tab, and then click the button that says 'Show Source'. Copy that form and paste the information in the box above.
In Eudora open the message, and click on the 'blaa blaa blaa' button. Copy and paste the whole message above.
For other email clients, please check 'Full Headers' in the help section.