sendmail connection reset message

[dhottinger at harrisonburg.k12.va.us]

I am having some problems with sendmail on a FC 6 machine.  When  
sending emails to a certain domain:dynavoxtech.com I get a connection  
timed out in my logwatch files.  Here is a snippet from my maillog:
Apr 18 13:37:57 mail sendmail[17274]: l3IHbv4T017274: Milter: no active filter
Apr 18 13:37:57 mail sendmail[17274]: l3IHbv4T017274: --- 220  
mail.harrisonburg.k12.va.us ESMTP Sendmail 8.13.8/8.13.8; Wed, 18 Apr  
2007 13:37:57 -0400
Apr 18 13:37:57 mail sendmail[17274]: l3IHbv4T017274: <-- EHLO  
mail.harrisonburg.k12.va.us
Apr 18 13:37:57 mail sendmail[17274]: l3IHbv4T017274: ---  
250-mail.harrisonburg.k12.va.us Hello localhost [127.0.0.1], pleased  
to meet you
Apr 18 13:37:57 mail sendmail[17274]: l3IHbv4T017274: ---  
250-ENHANCEDSTATUSCODES
Apr 18 13:37:57 mail sendmail[17274]: l3IHbv4T017274: --- 250-PIPELINING
Apr 18 13:37:57 mail sendmail[17274]: l3IHbv4T017274: --- 250-8BITMIME
Apr 18 13:37:57 mail sendmail[17274]: l3IHbv4T017274: --- 250-SIZE
Apr 18 13:37:57 mail sendmail[17274]: l3IHbv4T017274: --- 250-DSN
Apr 18 13:37:57 mail sendmail[17274]: l3IHbv4T017274: --- 250-ETRN
Apr 18 13:37:57 mail sendmail[17274]: l3IHbv4T017274: --- 250-AUTH LOGIN PLAIN
Apr 18 13:37:57 mail sendmail[17274]: l3IHbv4T017274: --- 250-DELIVERBY
Apr 18 13:37:57 mail sendmail[17274]: l3IHbv4T017274: --- 250 HELP
Apr 18 13:37:57 mail sendmail[17274]: l3IHbv4T017274: <-- MAIL  
From:<dhottinger at harrisonburg.k12.va.us> SIZE=4160  
AUTH=dhottinger at harrisonburg.k12.va.us
Apr 18 13:37:57 mail sendmail[17274]: l3IHbv4T017274: --- 250 2.1.0  
<dhottinger at harrisonburg.k12.va.us>... Sender ok
Apr 18 13:37:57 mail sendmail[17274]: l3IHbv4T017274: <-- RCPT  
To:<Jason.Smith at dynavoxtech.com>
Apr 18 13:37:57 mail sendmail[17274]: l3IHbv4T017274: --- 250 2.1.5  
<Jason.Smith at dynavoxtech.com>... Recipient ok
Apr 18 13:37:57 mail sendmail[17274]: l3IHbv4T017274: <-- DATA
Apr 18 13:37:57 mail sendmail[17274]: l3IHbv4T017274: --- 354 Enter  
mail, end with "." on a line by itself
Apr 18 13:37:57 mail sendmail[17274]: l3IHbv4T017274:  
from=<dhottinger at harrisonburg.k12.va.us>, size=4333, class=0,  
nrcpts=1,  
msgid=<20070418133756.1d8333rpwscckw00 at webmail.harrisonburg.k12.va.us>,  
proto=ESMTP, daemon=MTA, relay=localhost [127.0.0.1]
Apr 18 13:37:57 mail sendmail[17274]: l3IHbv4T017274: --- 250 2.0.0  
l3IHbv4T017274 Message accepted for delivery
Apr 18 13:37:57 mail sendmail[17273]: l3IHbvP3017273:  
to=Jason.Smith at dynavoxtech.com,  
ctladdr=dhottinger at harrisonburg.k12.va.us (48/48), delay=00:00:00,  
xdelay=00:00:00, mailer=relay, pri=34160, relay=[127.0.0.1]  
[127.0.0.1], dsn=2.0.0, stat=Sent (l3IHbv4T017274 Message accepted for  
delivery)
Apr 18 13:37:57 mail sendmail[17277]: l3IHbv4T017274: SMTP outgoing  
connect on mail.harrisonburg.k12.va.us
Apr 18 13:42:57 mail sendmail[17277]: l3IHbv4T017274: timeout waiting  
for input from mail01.dynavoxtech.com. during client greeting
Apr 18 13:42:57 mail sendmail[17277]: l3IHbv4T017274:  
to=<Jason.Smith at dynavoxtech.com>,  
ctladdr=<dhottinger at harrisonburg.k12.va.us> (3548/3548),  
delay=00:05:00, xdelay=00:05:00, mailer=esmtp, pri=124333,  
relay=mail01.dynavoxtech.com. [12.46.232.41], dsn=4.0.0,  
stat=Deferred: Connection timed out with mail01.dynavoxtech.com.

I turned the sendmail logging up so I could see what was occuring.  On  
the other end they are seeing this:

204.111.40.3-53920:04182007 10:30:25:Client #76 - 204.111.40.3:53920
204.111.40.3-53920:04182007 10:30:25:Accepted connection on <10.16.1.40>
204.111.40.3-53920:04182007 10:30:25:Channels VIP:  id=<0>,
name=<Default Virtual Host>, network_active=<1>, Secure Flag=0
204.111.40.3-53920:04182007 10:30:25:Relay ----><0>
204.111.40.3-53920:04182007 10:30:25:Trace - ('EXCEPTION',
('/build/smb6-5-patch1-HF7/ct/common/apps/python/lib/python2.3/socket.py
', 'recv', '212'), 'error', (54, 'Connection reset by peer'),
'[/build/smb6-5-patch1-HF7/ct/common/src/pythonframework/any_channel.py|
GetData|285]
[/build/smb6-5-patch1-HF7/ct/common/apps/python/lib/python2.3/socket.py|
recv|212]')

notice the connection reset by peer. It shows that they are closing the
connection.

My question is twofold.  One is this problem occuring on my mailserver  
or on their end?  and Two: if it is my problem,what is the issue and  
how can I fix it.  They are running an ironmail security appliance  
from SecureComputing.
-- 
Dwayne Hottinger
Network Administrator
Harrisonburg City Public Schools