We have had this issue since the Air Force had changed their MX records for their domain. It started as a 550 Host Unknown but the work around was adding a static path to the Route.cfg file. That lasted for a while and now fails with a 450. All the research I had done pointed towards the DNS as the issue but that is not the case. We had an independent consultant come in and confirmed that it is related to the GWIA.
I have read many threads so I know I am not the only one with that has come across this issue. I just haven't been able to find a fix.
Thank you in advance for the help!