I'm getting random emails being rejected from different client systems it seems.
I host my own Exchange 2010 server. FQDN mail.sosrad.com
Here is a copy of the rejected email / NDR
DB3EHSMHS017.bigfish.com rejected your message to the following e-mail addresses:
BOYLAN MEDICAL ASSOC-BROWNING, 310 (email@example.com) <mailto:firstname.lastname@example.org>
DB3EHSMHS017.bigfish.com gave this error:
A problem occurred during the delivery of this message to this e-mail address. Try sending this message again. If the problem continues, please contact your helpdesk.
Diagnostic information for administrators:
Generating server: Atlas.sos.local
DB3EHSMHS017.bigfish.com #500 Firewall Error ##
Original message headers:
Received: from sosrad.com (220.127.116.11) by mail.sosrad.com (18.104.22.168) with Microsoft SMTP Server id 14.0.722.0; Mon, 31 Oct 2011 11:16:42 -0400
From: Southeastern Overread Services <email@example.com>
To: "BOYLAN MEDICAL ASSOC-BROWNING, 310" <firstname.lastname@example.org>
Subject: Patient Report
Date: Mon, 31 Oct 2011 11:16:42 -0400
Received-SPF: None (savers.sos.local: email@example.com does not designate permitted sender hosts)
A few things that jump out at me...
1 Line 24: It looks like my internal .local address is being used (atlas.sos.local) as my generating server. When I check the send connected, the FQDN is listed as mail.sosrad.com
2 Line 44: The "Received-SPF" at the very bottom is listing the "savers.sos.local" as not being a designated sender... savers.sos.local is a NLB Cluster I run on my network of 2 servers and in no way is sending out any type of email.