When calling pbx1 -> iax trunk -> pbx2 -> sip provider I receive the following error

------------------------------------
    -- Accepting UNAUTHENTICATED call from 66.244.182.12:
       > requested format = gsm,
       > requested prefs = (),
       > actual format = gsm,
       > host prefs = (),
       > priority = mine
    -- Executing [92565395000@pbx1_iax:1] Macro("IAX2/pbx1_iax-2", "trunkdial|SIP/trunk_1/12565395000") in new stack
    -- Executing [s@macro-trunkdial:1] Set("IAX2/pbx1_iax-2", "CALLERID(num)=8473421095") in new stack
    -- Executing [s@macro-trunkdial:2] Set("IAX2/pbx1_iax-2", "CALLERID(name)=Adesso") in new stack
    -- Executing [s@macro-trunkdial:3] Dial("IAX2/pbx1_iax-2", "SIP/trunk_1/12565395000") in new stack
    -- Called trunk_1/12565395000
    -- Got SIP response 604 "Does not exist anywhere" back from 192.168.25.212
  == Everyone is busy/congested at this time (1:0/0/1)
    -- Executing [s@macro-trunkdial:4] Goto("IAX2/pbx1_iax-2", "s-CHANUNAVAIL|1") in new stack
    -- Goto (macro-trunkdial,s-CHANUNAVAIL,1)
    -- Executing [s-CHANUNAVAIL@macro-trunkdial:1] NoOp("IAX2/pbx1_iax-2", "") in new stack
    -- Timeout on IAX2/pbx1_iax-2
  == CDR updated on IAX2/pbx1_iax-2
    -- Executing [t@pbx1_iax:1] Congestion("IAX2/pbx1_iax-2", "") in new stack
  == Spawn extension (pbx1_iax, t, 1) exited non-zero on 'IAX2/pbx1_iax-2'
    -- Hungup 'IAX2/pbx1_iax-2'
voip*CLI>

--------------------------------
When dialing directly via pbx2  the call goes out fine over the sip trunk so I don't believe its any configuration problems on the outbound provider side of things. 



calling box,  relevant configuration
-------------- extensions.conf

[default]
exten => _9NXXNXXXXXX,1,Dial(IAX2/pbx2_iax/${EXTEN})
exten = _X.,1,Goto(lookupdundi|${EXTEN}|1)



remote box relevant configuration
-------------- extensions.conf
[default]
exten = _9NXXNXXXXXX,1,Goto(numberplan-custom-1|${EXTEN}|1)
exten = 8000,1,MeetMe(${EXTEN}|MsI)
exten = 8888,1,VoicemailMain(${CHANNEL:4:4})
exten = o,1,Goto(default|4143|1)
exten = 4140,1,Goto(ringroups-custom-1|s|1)
exten = 4141,1,Goto(ringroups-custom-3|s|1)
exten = 4142,1,Goto(ringroups-custom-2|s|1)
exten = 4143,1,Goto(ringroups-custom-4|s|1)
exten = 501X,1,Goto(lookupdundi|${EXTEN}|1)
exten = 502X,1,Goto(lookupdundi|${EXTEN}|1)
exten = 5031,1,Goto(lookupdundi|${EXTEN}|1)
exten = 5032,1,Goto(lookupdundi|${EXTEN}|1)

~~~~~~~~~~~~~~~~~~~~~~

[numberplan-custom-1]
plancomment = Adesso
include = default
include = parkedcalls
exten = _9NXXXXXX,1,Macro(trunkdial,${trunk_1}/${EXTEN:1})
comment = _9NXXXXXX,1,Local,standard
exten = _9847NXXXXXX,1,Macro(trunkdial,${trunk_1}/${EXTEN:4})
comment = _9847NXXXXXX,1,Local,standard
exten = _911,1,Macro(trunkdial,${trunk_1}/${EXTEN:0})
comment = _911,1,911,standard
exten = _91847NXXXXXX,1,Macro(trunkdial,${trunk_1}/${EXTEN:5})
comment = _91847NXXXXXX,1,Local,standard
exten = _91NXXNXXXXXX,1,Macro(trunkdial,${trunk_1}/${EXTEN:1})
comment = _91NXXNXXXXXX,1,Longdistance,standard
exten = _9NXXNXXXXXX,1,Macro(trunkdial,${trunk_1}/1${EXTEN:1})
comment = _9NXXNXXXXXX,1,Longdistance,standard
exten = _9011XXXXXXXX!,1,Macro(trunkdial,${trunk_1}/${EXTEN:1})
comment = _9011XXXXXXXX!,1,International,standard
exten = t,1,Congestion