Here is my sample configuration (edits for company sensitive information).
What I have observed during my debugging is that there is some logic that attempts to resolve the SIP-SERVER PRIMARY hostname. And in my scenario the hostname is not resolvable which is common from time to time. How can I disable that logic and have the unit just utilize the outbound proxy for all it's signaling.
Here is the error i see in the voice verbose debug output:
adtran ERROR! Could not resolve SIP server after resolving outbound-proxy
Re: Total Access 908 : Voice Trunk Type SIP : SIP Server w/ outbound proxy
You can add a static hostname as follows in global config mode:
host sbc.example.com <IP address>
host sbc.example.com 192.168.1.254
One caution: In many redundancy scenarios, a special DNS entry called an "SRV record" is used to resolve names used for specific services such as SIP. This entry is more than a hostname to IP mapping. It provides for failover and load balancing. If in your case "sbc.example.com" resolves to a single IP then this won't be an issue.
The ideal situation would be to fix whatever is broken with DNS.