550 Unrouteable address Problem

Hello Everybody,

Well i've installed Exim4 in an Ubuntu Machine to use it as a mail server. I have Gateway that activate Wifi-community only if it sends an e-mail and receives a positive answer from the SMTP mail server.

Well the probleme now, is that when the box tries to send the mail like this "wificom@L2TPServer" the Exim returns "550 Unrouteable address".

I've made these changes:
- Changing the /etc/hostname and /etc/hosts to L2TPServer.
- Putting L2TPServer as an FQDN in /etc/mailname.

But still the same probleme. PLZ refer me if there is a specific configuration in the Exim4 Server. Please Help.