For a couple months now we have been unable to send email to one particular domain. This is a client of ours and it makes it difficult to communicate between two project managers. I hoped it was a glitch and let it go for a while. A couple weeks later we had our Exchange 2003 server assessed for health and a few things were "repaired" that solved an unrelated problem but it did not solve the sending issue.
That is when I solicited help from the IT department of our client. As I expected, they said it must be on our end because they have no trouble receiving email from anyone else. And we have no problem sending to anyone else. Plus they were moving to a new location and that delayed things a couple more weeks.
I then solicited help from our service provider who couldn't discern the problem but suggested that our client add our domain name to the "allowed senders list" in mxlogic that they use for spam control. Our client added our name to the allow senders list and messages that were sitting in our queue for their domain were immediately delivered to them. Great! I thought. I sent a response to them and it sat in the queue for at least a day and then was delivered sometime over the weekend. Now i have sent another email to them and once again the email is sitting in our SMTP queue in delayed status. The queue information says "The remote server did not respond to a connection attempt". It seems like their server is not accepting requests for mail delivery from our server.
If I send a tracert to their email server I see multiple time outs before it then goes on to complete the trace. Could that be happening to the emails? Could it be that their server can't talk back to ours to validate? Isn't that the normal process for email delivery?