Our domain can't send email to one particular domain. We are running Exchange Server 2003. I have some information about the receiving domain, but not all. One thing I know about their email system is that they recently added a Barracuda firewall. On our Exch Server I ran an NSLookup, and I see their MX records just fine. I've done a manual Telnet test to their mail exchanger, and the test begins okay, but tends to "time out" after awhile. After entering each line item of the Telnet test, the responses back from their end tend to lag significantly, and at random points during these tests, the session will error out with a "Connection to host lost" error.
I've run Telnet tests to other domains that we send email to, and the tests complete fine.
A significant element of this issue (I think?) is that this particular domain is the host of our web site.
Again, I'm not at the site we are sending email to, and I have limited contact with them and how their system is set up, but if anyone can suggest things that might solve this, that would be great.