MTA server name (MX) appended to sender address

[det]

Hi there,

anyone knows why the MX server hostname would be appended to the sender email address?

the email was sent by a fax machine. the 'envelope-from' address is reflecting the correct sender address but the email itself has wrong 'from' address.

email header as below.


Received-SPF: Neutral (access neither permitted nor denied) identity=mailfrom; client-ip=203.92.x.x; helo=svr1.mydomain.com; envelope-from=sendername@senderdomain.com; receiver=support@mydomain.com
Received: from svr1.mydomain.com (mail.mydomain.com [203.92.x.x])
by svrmx1.mydomain.com (Postfix) with ESMTP id 5AD6976038
for <support@mydomain.com>; Sun, 27 Mar 2011 14:47:39 +0800 (SGT)
Received: from RNPE14F69 (unknown [119.75.x.x])
by svr1.mydomain.com (Postfix) with ESMTP id 5FB68D8B
for <support@mydomain.com>; Sun, 27 Mar 2011 14:47:38 +0800 (SGT)
From: RicohMPC4500@svrmx1.mydomain.com