We started having problems emailing to an external domain. This started happening about a month ago. Prior to that we didn't have any problems emailing to the same domain. We are not having any problem sending to other domains. First we get a 'delay' notification back with SMTP 4.4.7, then we get a return notification of failure. I can connect to the other domain through Telnet but it's not accepting other commands. But I do get this weird response back with 220. I also see the same thing when I look at the email in Exchange System Manager in Tracking. I've attached a file that shows this message. One thing I haven't been able to do because the user deleted them is look at the message header on the returned 'failure' email.
They white listed us in their Barracuda. That didn't clear things up. I'm not seeing anything on my end that would indicate an issue. I've looked through the message logs and don't find anything unusual there. They've talked to their ISP who is telling them that they're not seeing our email - not sure how reliable this information is since it's second hand.