Friend using my email address

I don't think my friend knows he's doing this, as he's very new to computers and the Net, but somehow when I get email from him, it's coming from my own email address, but going to the same email address. I can verify that by checking the individual message's properties as shown below:

Message-ID: <20020322173844.3c9b6c24024f1@hotmail.com>
X-Originating-IP: [xx.xx.xxx.xx]
From: "Daxxxxx" <exxxxx_gxxxxxxx@hotmail.com>
To: <Exxxxx_gxxxxxxx@hotmail.com>
Subject: Emailing: YOU
Date: Fri, 22 Mar 2002 13:38:09 -0600
MIME-Version: 1.0
Content-Type: multipart/mixed;
boundary= "----=_NextPart_000_000E_01C1D1A6.CE086EC0 "
X-Priority: 3
X-MSMail-Priority: Normal
X-Mailer: Microsoft Outlook Express 6.00.2600.0000
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600.0000

I changed some things to protect the innocent, but take my word for it, somehow he's using my address and sending stuff to that address. I know he wouldn't do it on purpose and must've happened by accident. How can this be happening?

 

Maybe he's set your address as the "Reply-To" default in OE?