Hi all! 

I really don't know why "Mitel" rejects my calls. I'm using Kamailio to forward calls to Mitel. 

A little more graphic:

Please see the picture:

http://s3.subirimagenes.com:81/otros/5226539form.jpg

SIP PHONE (Linksys)   ---> Kamailio (1.5.4) ----> Mitel ----> Mitel Phone

Mitel rejects my calls with "404 Not Found". Ok, you may think: "the extension that you are calling doesn't exists".. please dont think that. 

(One more thing: If I try to make the same scene using Asterisk instead Kamailio everything works fine.)

So, I made a sip capture to see what happens: 
Sip Phone -> 100 
192.168.10.140 -> Sip Phone 
192.168.10.150 -> Kamailio 
192.168.10.160 -> Mitel 
Mitel Phone -> 200 

Kamailio
U 192.168.10.140:5060 -> 192.168.10.150:5060 
INVITE sip:200@192.168.10.150 SIP/2.0. 
Via: SIP/2.0/UDP 192.168.10.140:5060;branch=z9hG4bK-d063d53a. 
From: "Sip Phone" <sip:100@192.168.10.150>;tag=d396005aaf3ab9a2o0. 
To: "Mitel Phone" <sip:200@192.168.10.150>. 
Call-ID: d4de30ba-eb6944c2 [!at] 192.168.10.140 (replace the [!at] with a @). 
CSeq: 101 INVITE. 
Max-Forwards: 70. 
Contact: "Sip Phone" <sip:100@192.168.10.140:5060>. 
Expires: 240. 
User-Agent: Linksys/SPA941-5.1.8. 
Content-Length: 395. 
Allow: ACK, BYE, CANCEL, INFO, INVITE, NOTIFY, OPTIONS, REFER. 
Supported: replaces. 
Content-Type: application/sdp. 

U 192.168.10.150:5060 -> 192.168.10.140:5060 
SIP/2.0 100 Giving a try. 
Via: SIP/2.0/UDP 192.168.10.140:5060;branch=z9hG4bK-d063d53a;rport=5060;received=192.168.10.140. 
From: "Sip Phone" <sip:100@192.168.10.150>;tag=d396005aaf3ab9a2o0. 
To: "Mitel Phone" <sip:200@192.168.10.150>. 
Call-ID: d4de30ba-eb6944c2 [!at] 192.168.10.140 (replace the [!at] with a @). 
CSeq: 101 INVITE. 
Server: Kamailio (1.5.4-notls (i386/linux)). 
Content-Length: 0. 

U 192.168.10.150:5060 -> 192.168.10.160:5060 
INVITE sip:200@192.168.10.150 SIP/2.0. 
Via: SIP/2.0/UDP 192.168.10.150;branch=z9hG4bKc17.8e746ba.0. 
Via: SIP/2.0/UDP 192.168.10.140:5060;rport=5060;received=192.168.10.140;branch=z9hG4bK-d063d53a. 
From: "Sip Phone" <sip:100@192.168.10.150>;tag=d396005aaf3ab9a2o0. 
To: "Mitel Phone" <sip:200@192.168.10.150>. 
Call-ID: d4de30ba-eb6944c2 [!at] 192.168.10.140 (replace the [!at] with a @). 
CSeq: 101 INVITE. 
Max-Forwards: 69. 
Contact: "Sip Phone" <sip:100@192.168.10.140:5060>. 
Expires: 240. 
User-Agent: Linksys/SPA941-5.1.8. 
Content-Length: 395. 
Allow: ACK, BYE, CANCEL, INFO, INVITE, NOTIFY, OPTIONS, REFER. 
Supported: replaces. 
Content-Type: application/sdp. 

U 192.168.10.160:5060 -> 192.168.10.150:5060 
SIP/2.0 100 Trying. 
Via: SIP/2.0/UDP 192.168.10.150;branch=z9hG4bKc17.8e746ba.0,SIP/2.0/UDP 192.168.10.140:5060;rport=5060;received=192.168.10.140;branch=z9hG4bK-d063d53a. 
From: "Sip Phone" <sip:100@192.168.10.150>;tag=d396005aaf3ab9a2o0. 
To: "Mitel Phone" <sip:200@192.168.10.150>;tag=0_4044193584-65506210. 
Call-ID: d4de30ba-eb6944c2 [!at] 192.168.10.140 (replace the [!at] with a @). 
CSeq: 101 INVITE. 
Content-Length: 0. 

U 192.168.10.160:5060 -> 192.168.10.150:5060 
SIP/2.0 404 Not Found. 
Via: SIP/2.0/UDP 192.168.10.150;branch=z9hG4bKc17.8e746ba.0,SIP/2.0/UDP 192.168.10.140:5060;rport=5060;received=192.168.10.140;branch=z9hG4bK-d063d53a. 
From: "Sip Phone" <sip:100@192.168.10.150>;tag=d396005aaf3ab9a2o0. 
To: "Mitel Phone" <sip:200@192.168.10.150>;tag=0_4044193584-65506210. 
Call-ID: d4de30ba-eb6944c2 [!at] 192.168.10.140 (replace the [!at] with a @). 
CSeq: 101 INVITE. 
Contact: <sip:192.168.10.160>. 
Content-Length: 0.

This is my Kamailio code from reenvites.. 
route[4] { 
        t_relay("udp:192.168.10.160:5060"); 
        t_on_reply("1"); 
        exit; 

If you pay attention to INVITES (Kamailio SIP messages) you will see:

From: "Sip Phone" <sip:100@192.168.10.150>;tag=d396005aaf3ab9a2o0. 
To: "Mitel Phone" <sip:200@192.168.10.150>.

I think that should be:

From: "Sip Phone" <sip:100@192.168.10.150>;tag=d396005aaf3ab9a2o0. 
To: "Mitel Phone" <sip:200@192.168.10.160>.

It could be the reason for Mitel rejects? Can I fix it? I can use TEXTOPS but I cant understand why Mitel rejects the Kamailio INVITES.

I will thanks any help!