GW 8.0.4-We have a situation that affects only one person who sends email to
us, all other incoming email is fine. Oddly, if this person sends email to
one individual, it arrives fine. Most of her email has a very large
distribution list (NJ court system)-but this is not usual here, we receive
email from many sources that have very large distribution lists just fine.
Before mid-September, her emails arrived fine (no changes here at that
time). We are a Postini customer, and their logs mark the email as
delivered to us but there is no trace of it in any or our logs. It does not
seem to matter which email address in our system she puts in the
distribution list either. I have checked for client rules, black list
setting and can find nothing in our firewall logs either. Google/Postini
has categorically stated this is not an issue with their service despite the
fact that the message is from The undeliverable
that goes back to the sender has the following error:

From: Mail Delivery System []
Sent: Tuesday, December 17, 2013 10:32 AM
To: Linda xxxx
Subject: Undeliverable: xxxx
Delivery has failed to these recipients or groups:
4723119138 <mailto:>
A problem occurred during the delivery of this message. Please try to resend
it later.
Diagnostic information for administrators:
Generating server:
#< #4.4.2 X-Postfix; lost connection with our IP[our IP] while sending
message body> ##

Any ideas where to look would be much appreciated.
TIA for reading this.