I have been running qmail for about 8 months, It works great.
So far I have not been able to resolve on problem.
When an smtp connection comes in we only want to connect
with servers who have forward and reverse DNS that match.
I managed to install a macro into sendmail (mail server we replaced)
in about 15 minutes that takes the IP of the incoming smtp request
looks up the name, then looks up the IP for the NAME. the IP
should be the same as the connecting host. If this is not the case
the smtp connection should be dropped.
I use tcpserver to start smtpd.
I use the -p (paranoid) option, (added the option a few days ago)
which by my preliminary understanding was supposed to accomplish
this task of DNS cross-matching.
However I receieved an email recently whois headers are
Received: from unknown (HELO www.somang.or.kr) ([EMAIL PROTECTED])
I noticed that there isn't a hostname.
nslookup 211.38.3.100 will return no hostname.
So back to the drawing board.
http://cr.yp.to/ucspi-tcp/tcpserver.html ( <-- drawing board)
I notice -p: Paranoid. After looking up the remote host name in DNS, look up
the IP addresses in
DNS for that host name, and remove the environment variable
$TCPREMOTEHOST if none of the addresses match the client's IP address.
upon re-reading this option I notice it did what it says it does,
It removed the $TCPREMOTEHOST, hence the "Received: from unknown "
I still got the email. So now I figure that $TCPREMOTEHOST is
passed to smtpd in the environment variables.
so somehow I need to tell smtpd to close
if "condition" is not met.
Oh.. I have read the man pages. I have installed qmail, vpopmail,
on more than a dozen
servers for nearly that many clients. I understand quite abit.
David Killingsworth.
