On my wife's computer running OS X Yosemite and Apple Mail, when she sends an email her address is being changed from firstname.lastname@example.org to email@example.com. This started to happen when she changed from pop to map for incoming mail. cds053.dcs.int.inet is an internal mail server in the shaw network. That computer not the domain is set up anywhere in her computer. I also believe that I have seen the address xxxxx@cds035,dcs.int.inet (but can't find the copy of the email with the headers). The strange thing is the changed to email domain is always the last received from mail server. The following headers show the change, this email left her computer with her correct address firstname.lastname@example.org.
Received: from cds053.dcs.int.inet (LHLO cds053.dcs.int.inet) (10.0.145.136)
by cds053.dcs.int.inet with LMTP; Sun, 25 Jan 2015 12:54:46 -0700 (MST)
Received: from pd7ml2no-ssvc.prod.shaw.ca (pd7ml2no-ssvc.prod.shaw.ca [10.0.153.162])
by cds053.dcs.int.inet (Postfix) with ESMTP id ADA6B7D804C
for <email@example.com>; Sun, 25 Jan 2015 12:54:46 -0700 (MST)
X-Cloudmark-SP-Result: v=1.1 cv=YzkDeCCLkfvKKKvhMilE7Ce3LEB3kVshiYMlAyNVURc= c=1 sm=1
a=Scg_NR0Usi0A:10 a=BLceEmwcHowA:10 a=kj9zAlcOel0A:10
a=AxtXhqurj2nclCuvmOwhBA==:17 a=uCCo4La6iGOqyqK8QO8A:9 a=CjuIK1q_8ugA:10
Received: from unknown (HELO [10.0.1.90]) ([184.108.40.206])
by smtp-out-05.shaw.ca with ESMTP; 25 Jan 2015 12:54:46 -0700
From: XXXX XXXXXXXX <firstname.lastname@example.org>
Content-Type: text/plain; charset=us-ascii
Subject: Does this look any better?
Date: Sun, 25 Jan 2015 11:54:46 -0800
To: YYY YYYY <email@example.com>
Mime-Version: 1.0 (Mac OS X Mail 8.1 \(1993\))
X-Mailer: Apple Mail (2.1993)
The people she emails can not reply or send to this changed address. Last week I spent 3.5 hours on the chat service trying to get this fixed and there only response was switch to Thunderbird but that doesn't work for her. Has anyone seen this before and how was it fixed?