451-4.4.0 Primary Target IP Responded With ESMTP Service Not Available
Posted on 2016-10-13
One of my clients has an issue being unable to send to a specific email address, they are running SBS 2008 and each time they attempt to send an email to address in the question, the message sits in the exchange queue and fails to send. I looked in Exchange Message Console and can see the following error is listed against the relevant queue "451-4.4.0 Primary Target IP Responded with: "554-gmx.net (mxgmx002) Nemesis ESMTP Service Not Available"
I have tested sending mail from my account and the recipient receives the email without any issues.