SIP
439 First Hop Lacks Outbound Support
The first outbound proxy does not support the SIP outbound mechanism (RFC 5626) that the UA is trying to use.
जब आप यह कोड देखें
When a UA configured for SIP outbound connects to a proxy that doesn't support the outbound option-tag.
कैसे ठीक करें
Upgrade the outbound proxy to support RFC 5626, or configure the UA to not require outbound support.