I use the below configuration for my SIP trunk.
They do mention that qualify should be "no"
THEY DO MENTION THE FOLLOWING ON THEIR SUPPORT PAGE:
"Enclosed the necessary settings to configure to Asterisk for sipgate. (Very important to have the SIP ID at the end of the register command) sip.conf [general] port = 5060 bindaddr = 0.0.0.0 context = error qualify=no disallow=all allow=alaw allow=ulaw allow=g729 allow=gsm allow=slinear srvlookup=yes register =>"
But this works......
Outbound Caller ID: "Your Name"
Maxium channels: 2
Trunk Name: Sipgate DE
PEER Details:
username=
type=peer
secret= (you can find your SIP password when logged in to your acount here: https://secure.sipgate.de/user/configreader.php?show_conf=gxp2000)
qualify=yes
insecure=very
host=sipgate.de
fromuser=
fromdomain=sipgate.de
dtmfmode=RFC2833
disallow=all
context=from-trunk
canreinvite=yes
authuser=
allow=alaw&ulaw&G.726&gsm&g729&g723
port=5060
USER Context:
USER Details:
username=
type=friend
secret= (you can find your SIP password when logged in to your acount here: https://secure.sipgate.de/user/configreader.php?show_conf=gxp2000)
qualify=yes
insecure=very
host=sipgate.de
dtmfmode=RFC2833
disallow=all
context=from-trunk
canreinvite=yes
allow=alaw&ulaw&G.726&gsm&g729&g723
port=5060
Register String: