Outlook Test Message sent automatically

[jt1001]

I received two "Microsoft Office Outlook Test Message" e-mails which read "This is an e-mail message sent automatically by Microsoft Office Outlook's Account Manager while testing the settings for your POP3 account." This was sent overnight, automatically.

I know that this message is normally sent when I set up the account, but I have had this account for some time now, and it was sent when I not at my computer. Is someone trying to hack into my system?

Using:
Outlook 2002 SP3
Windows XP Home Edition, Version 2002, SP2
Dell Dimension 8400

Thank you!

[jt1001]

Update:

I analyzed the headers a little bit more. I compared header to an e-mail I sent to myself and found a discrepancy in the "Received" line.

Known e-mail header:
Received: from jt (pool-71-106-178-20.lsanca.dsl-w.verizon.net [71.106.178.20])
(Authenticated sender: jt@troen.com)
by sc1-out06.emaildefenseservice.com (Postfix) with ESMTP
for <jt@troen.com>; Wed, 28 Nov 2007 18:41:44 +0000 (UTC)

Suspect header:
Received: from TORCC006 (unknown [10.0.63.29])
(Authenticated sender: jt@troen.com)
by sc1-out01.emaildefenseservice.com (Postfix) with ESMTP
for <jt@troen.com>; Tue, 27 Nov 2007 14:54:57 +0000 (UTC)

It appears to be from an unknown IP address, though still authenticated as me. Any ideas?

Thanks!