[general]
context=default 
port=5060                       
bindaddr=0.0.0.0               
externip = 212.xxx.xxx.xxx
srvlookup=yes   


[798]
type=friend
secret=xxxxx
mailbox=798
nat=yes
host=212.yyy.yyy.yyy  ; my rmote ip at home
context=DFSA
callerid=RSHome [798]
dtmfmode=rfc2833


the conversation look sright on the CLI

Verbosity is at least 12
    -- Executing Dial("SIP/798-69b2", "sip/790|5") in new stack
    -- Called 790
    -- SIP/790-8329 is ringing
    -- SIP/790-8329 is ringing
    -- SIP/790-8329 is ringing
    -- SIP/790-8329 is ringing
    -- Nobody picked up in 5000 ms
    -- Executing VoiceMail("SIP/798-69b2", "u790") in new stack
    -- Playing 'vm-theperson' (language 'en')
    -- Playing 'digits/7' (language 'en')
    -- Playing 'digits/9' (language 'en')
    -- Playing 'digits/0' (language 'en')
    -- Playing 'vm-isunavail' (language 'en')
    -- Playing 'vm-intro' (language 'en')
    -- Playing 'beep' (language 'en')


but no audio is heard ...

tcpdump of the packets shows them heading off to local network 192.168.1.xxx instead of 212.18.xxx.xxx

the packets on 5060 etc go the right places.