Fabien GARZIANO wrote:
>  And for dns, I'm sorry, I typed it too fast and when I meant no 'dns' i
>  also meant no 'named' process. 

On mail servers it's usually a good idea to run a local nameserver, even 
if you have no zone files to publish (e.g., the "caching nameserver" 
named configuration that comes with RedHat-flavored distributions). 
Without a local nameserver you have to make a request against the ISPs 
servers for every message you receive.  If you run a local, caching 
server, once you've looked up an address it's kept locally which improves 
performance on a busy mail server.

If you run a caching server, make sure that /etc/resolv.conf has 
127.0.0.1 as its initial nameserver address.  Add the ISPs addresses 
below this in case your local named falls over.

Peter