I'm testing music on hold with the 504g with firmware version 7.4.4
When the music on hold server is set and hold is pressed INVITEs to the moh server are sent directly to the IP address returned on an A record lookup of the moh server. The phone is configured to use an outbound proxy for all predialog and in dialog requests ("Use Outbound Proxy" & "Use OB Proxy In Dialog" both set to "yes")
This bug is nearly identical to one I posted previously for the SPA 942 (see thread https://supportforums.cisco.com/message/3125394 and resultant defect number CSCte64251)
Attached is a pcap of the 504g (email@example.com) on a call with an eyebeam (firstname.lastname@example.org). erick.1 puts enoch on hold through the outbound proxy and then begins inviting email@example.com but instead of sending the invites through the proxy, it sends them directly to the A record for beta.junctionnetworks.com. The 504g is also configured to do DNS SRV lookups but it doesn't seem to do those for anything other than the proxy.
Please confirm that this is an issue.