[ On Wednesday, October 31, 2001 at 10:37:20 (-0800), Marc MERLIN wrote: ]
> Subject: Re: [Exim] RFC ?
>
> Note that of course nothing says that the IP literal or the FQDN have to be
> resolvable or reachable by the receipient (in case you send a mail from
> behind a masquerading firewall)
No, nothing actualy _says_ that, but you can sure as heck imply that
from the ample context (i.e. the RFCs were writting in the mid to late
1980's _LONG_ before firewalls and NATs became anything more than
academic curiosities).
> So, if you try to validate the value given there, you will have surprises
> (it's a bit like ident, you can use the value for debugging if a meaningful
> one is given by the remote host, but you can't depend on it to accept mail)
No, the name given in the greeting MUST be THE canonical hostname for
the client originating the connection and from this you can assume that
it MUST be a name that resolves to at least an A RR that has the same
target address as the source address of the connection. If that's not
possible then the client may use a literal representatio of its source
IP address.
DO NOT RUN SMTP THROUGH A NAT IF YOU CAN'T GET THE DNS RIGHT!!!! Use an
application level gateway!!!!
--
Greg A. Woods
+1 416 218-0098 VE3TCP <gwoods@???> <woods@???>
Planix, Inc. <woods@???>; Secrets of the Weird <woods@???>
