Hi Francios 

Thank you for you recommend

from your recommendation, i add the host name : sip.yeah.com into the /etc/hosts

but i am still getting error on DNS 
 Failed with status DNS Error [503]

it seems that FS needs resolve the sip.yeah.com from the DNS server.
the FS support register with domain - domain is not real and the parameter = register-proxy. Is there the same paramater for make call out??

i do ping sip.yeah.com successfull but when i do nslookup and the DNS server response cannot find the domain name

[root@localhost external]# nslookup sip.yeah.com
Server:         8.8.8.8
Address:        8.8.8.8#53

** server can't find sip.yeah.com: NXDOMAIN

[root@localhost external]# ping sip.yeah.com
PING sip.yeah.com (118.69.239.250) 56(84) bytes of data.
64 bytes from sip.yeah.com (118.69.239.250): icmp_seq=2 ttl=250 time=6.84 ms

Thank you
Ha`