IP address for sender of hotmail message ?

[Jacques]

Look for "X-Originating-IP" in the mail headers.

If it's from behind a proxy server like gmail look for "Recieved: from " it will be between square brackets thus [127.0.0.1]

[Lizard]

Try some of these, they mask your ip address.

[Jacques]

You could telnet hotmail servers and send from there........

[Lizard]

Or!, you could work on the assumption that the person your mailing wouldn,t have a fucking clue what an IP address is, as it,s only a series of address,s used by a particular provider, and not a direct hotline to any individual.
Failing that use royal mail, and write with your feet.