I've observed that this PUBLISH is generated from Kamailio and sent to Kamailio but never is relayed to the end user. Also I'd like to mention that I'm using the MULTIDOMAIN mode.
Via: SIP/2.0/UDP 1.1.1.1;branch=z9hG4bK1155.b09d7f4.0
CSeq: 10 PUBLISH
Content-Length: 1486
User-Agent: kamailio (4.0.1 (i386/linux))
Max-Forwards: 70
Event: reg
Expires: 3601
Content-Type: application/reginfo+xml
<?xml version="1.0"?>
<reginfo xmlns="urn:ietf:params:xml:ns:reginfo" version="0" state="full">
<contact id="0xb36a5f88" state="active" event="registered" expires="1579" callid="Zjc3MTE2NTY1MDQ5NjA3NDVmNTdhOGU4NDVjNDI1NTU" cseq="4" received="sip:
182.189.2.135:36810" path="" user_agent="X-Lite release 4.5.2 stamp 70142">
<uri>sip:4144@182.189.2.135:36810;rinstance=93ea3ac79b5c8181</uri>
</contact>
<contact id="0xb36a6198" state="active" event="registered" expires="2775" callid="YzIyNDA1NzJkOWI4ZDA2YjdkYTk5NmU5MDA3YmEzMWE" cseq="2" received="sip:
199.255.209.166:49182" path="" user_agent="X-Lite release 4.5.2 stamp 70142">
<uri>sip:4144@10.254.168.28:49182;rinstance=f0f3b6fe4979841b</uri>
</contact>
<contact id="0xb36a64d8" state="active" event="registered" expires="2788" callid="ZDk3MmEzMmI3OGRmODUxODFlNzE4ODVkNTAxNDE3MjQ" cseq="4" received="sip:
199.255.209.166:49182" path="" user_agent="X-Lite release 4.5.2 stamp 70142">
<uri>sip:4144@199.255.209.166:49182;rinstance=9263a0c33eddcd04</uri>
</contact>
<contact id="0xb36b1168" state="active" event="created" expires="3600" callid="ZmQyNTA1Njg5NDExMzIwOTBmZmZhZDNjNTBjODUxNzk" cseq="4" received="sip:
199.255.209.166:17482" path="" user_agent="X-Lite release 4.5.2 stamp 70142">
<uri>sip:4144@199.255.209.166:17482;rinstance=5ccf1f2256f17489</uri>
</contact>
</registration>
</reginfo>
If only this could reach my user agent then I think the presence will work fine.