Getting calls directly to my asterisk with allowguest=yes

I want to be able to recieve calls directly when someone puts in my dynamic host name into a softphone like ekiga.

My sip.conf:

[general]
qualify=yes
allowguest=yes
context=sip-in
allow=all
srvlookup=yes
register => xxx:xxxA@sipgate.de/xxx
canreinvite=no
nat=no
externhost=my.dyn.dns
localnet=192.168.0.0/24

my ASterisk Box is connected directly to the internet and isn’t nated.

It works, the call reaches asterisk, my softphones in my LAN ring but after answering the call with a phone it’s dropped after a few seconds.
Asterisk says:

Maximum retries exceeded on transmission

Calls coming from Sipgate work just fine. Just this direct-Ip-dialing doesn’t seem to work.

Any ideas?

tnx.

Try nat=yes and see what happens. Your soft phone can be behind nat (or acting as such if you have a firewall on your computer).