Asterisk registration to Aastra MX-ONE

[uniwork]

Dear all;
I want to connect my Asterisk server to our company's Astra MX-ONE. The scenario is like this: when a user make outside call, MX-ONE forward call to Asterisk and Asterisk does something and then backwards call again to MX-ONE and MX-one connects user to the dialed number . When I configure sip trunk on Asterisk and reload sip.conf I get two errors:
1. Got 423 Interval too brief for service billing@192.168.2.75, minimum is 300 seconds
2. Got 404 Not found on SIP register to service billing@192.168.2.75, giving up

The ip address of Aastra MX-ONE is 192.168.2.75 and ip of Asterisk server is 192.168.2.158. I installed Asterisk on VirtualBox and its connected to Aastra MX-ONE . Here is the configuration of sip.conf:

[general]
register => tcp://billing@192.168.2.75

maxexpiry=5000
minexpiry=300
defaultexpiry=1000

[route_1]
type=friend
defaultuser=billing
fromuser=billing
context=incoming_route_1
host=192.168.2.75
insecure=invite
dtmfmode=rfc2833
disallow=all
allow=ilbc
allow=g729
allow=gsm
allow=alaw
allow=ulaw
qualify=yes
canreinvite=no

extensions.conf:

[incoming_route_1]

exten => _9.,1,NoOp()
.
.
.
same => n,Transfer(SIP/0${EXTEN:1}@route_1,30)

I changed the value of maxexpiry minexpiry and defaultexpiry but 423 error never goes away. Do I need any special config on both sides. I just put an arbitrary username for my asterisk server "billing" which I don't know is correct or not. I asked our Aastra MX-ONE Admin for any configuration on that side but he says there is no configuration on that side and all configuration should be on Asterisk side.
All configuration on MX-ONE side is something like:
sip:?@192.168.2.158 which is the ip of Asterisk
Any suggestion? Thanks in advance.