On a clients server running SBS 2011, I am unable to send mail to external domains. Previously they were using a smarthost send connector. The stopped paying for the connector, so today email stopped sending. I was unaware that they had the send connector, but after seeing the address as the next hop in the message queue, they mentioned it.
I disabled using smart host on the send connector, and set it to use DNS instead. I also tried recreating the send connector.
I then checked the message queue, and the external domains showed up. However, they end up with error:
451 4.4.0 Primary target IP address responded with *.* Atempted failover to alternate host but did not succeed.
I ran the mail flow troubleshooter, and got no errors until the following on Remote Delivery Queue SMTP Commands analysis results:
Remote server **** failed the mail acceptance test. RCPT TO command: Respond = 554 5.7.1 <******@*****.com>: Relay access denied
I am unsure where to go from here.