There is a way to do it. I came across this from a
listserv and tried it on a couple of e-mails. You will
need to decide whether or not this work-around will apply
on a message by message basis or whether you want modify
the template.
Open the message from Sent Items, then choose Tools,
Forms, Design This Form.
From the drop down box in the Field Chooser, select All
Mail Fields.
The BCC field should appear. Click and drag the BCC field
box over to the form and place it in an appropriate place
(i.e., under the CC field).
Right-click the newly placed BCC field and choose
Properties.
Click on the Validation tab.
Select the "Include this field for Printing and Save As"
checkbox.
Click OK.
Close the message and click 'Yes' when asked to save
changes.
Now when you open this message, you should be able to
print the BCC list.
This is the basic functionality. You can of course format
the BCC field on the form to match the other fields.
This works on a message by message basis (i.e., you'd have
to do this to each message in order to print the BCC
field). You may wish to modify the main template if you'd
like this feature available for every message.
Good luck!