Why does Outlook 2003 resize images when I paste them in emails?

When I copy an image from some other source, Outlook tries to scale it up
when I paste the image into an email. This is a big problem because the
image manipulation tools inside the email composer don't even provide a way
to scale height and width uniformly, nor do they offer any way to get back to
the original image pixel size. I expect to be able to send something with
pixel perfect accuracy, like Outlook used to do. Help offers no explanation
of this. It looks like I can't turn it off, but I figured I'd take one last
stab with online help.