I and my associate have done a few qmail installations. Followed the lwq documentation and usually worked like a charm.
But this time around we installed it on a PC with the following config
486DX2
16 MB RAM
600+ MB HDD
2 PCI 10/100 NIC
OS Vector Linux 4.0
It also serves as a firewall + NAT, running projectfiles.com firewall.
qmail will approx serve at the most about 10 accounts.
The problem we are facing is this, mail sent for example from yahoo fails with the following message

" Hi. This is the qmail-send program at yahoo.com.
I'm afraid I wasn't able to deliver your message to the following
addresses.
This is a permanent error; I've given up. Sorry it didn't work out.

<xxx@xxxx.com>:
Sorry, I wasn't able to establish an SMTP connection. (#4.4.1)
I'm not going to try again; this message has been in the queue too
long."

At the same time any mail originating from the very same mailserver is delivered without a problem.

From what we can make out it seems to be a problem with the smtp part of the mailserver. It is not responding to requests. I am able to send mail from within that static IP segment. I have access to another account with the same ISP on the same range. The mail is deilvered without a problem.
We have also checked with the ISP if they are blocking the port and the answer is no. I also think that no ISP blocks port 25/110. We also checked the MX record at the registrars and can't find any obvious problems. Have done a dig and nslookup of the MX too and can't find any problem.
I've also checked this via www.dnsstuff.com and not had any obvious errors
Only thing is that the dns lookup for the MX returns a MAIL .xxxx.com. Is this significant ?
Also why should it work within the same static range and not outside of it ?

I am really at me wits end !
All help appreciated.
Ashraf

I think you should try telnetting to your mail server from another machine on your network. Try this...

telnet yourdomain.com 25

Notice there is a space between the FQDN and the 25 which is the port number. You should get something like this...

[root@falcon root]# telnet yourdomain.com 25
Trying yourdomain.com...
Connected to yourdomain.com.
Escape character is '^]'.
220 hostname.yourdomain.com ESMTP
helo anything
250 hostname.yourdomain.com
mail from: you@yourdomain.com
250 ok
rcpt to: you@yourdomain.com
250 ok
data
354 go ahead
something blah,blah blah
.
250 ok 1090602878 qp 13724
quit
221 hostname.yourdomain.com
Connection closed by foreign host.

The helo, mail from, rcpt to, and data commands are commands you input yourself at the command line. When you're done typing the body of your message (like something, blah, blah etc) just put a single dot and hit enter to end the body section. Then type quit and the connection will be closed. Hopefully you should get all positive responses from your smtp server.

If you don't get a positive response from your SMTP server, then it could be a DNS problem. Maybe you're having trouble resolving your FQDN into an IP address. If you're able to get a banner string (the first 220 response above) then it means you're able to connect just fine, but it's a problem with configuration. Check your logs under /var/log/qmail/qmail-smtpd/current and see what it says. Also post your /var/qmail/supervise/qmail-smtpd/run file so we can see how you're running your smtp server.

This is what I get when I try a telnet from within the same internet IP range from a masq'd internal connection
220 mail.xxxxindia.com ESMTP
helo anything
250 mail.xxxxindia.com
mail from:
250 ok
rcpt to
250 ok
data
354 Please start mail input.
Mundane day isn't it .
quit
quit
.
250 Mail queued for delivery.
quit
221 Closing connection. Good bye.

Connection to host lost.


This is what I get when I try a telnet from an external internet IP !

login as: kmashr
Sent username "kmashr"
ashraf@20X.1X6.X71.XX7's password:
[ashraf@xxxxserv ashraf]$ telnet xxxxindia.com 25
Trying 21X.1X8.X55.XX6...

and hangs there


and here is the /var/qmail/supervise/qmail-smtpd/run file

#!/bin/sh

QMAILDUID=`id -u qmaild`
NOFILESGID=`id -g qmaild`
MAXSMTPD=`cat /var/qmail/control/concurrencyincoming`
LOCAL=`head -1 /var/qmail/control/me`

if [ -z "$QMAILDUID" -o -z "$NOFILESGID" -o -z "$MAXSMTPD" -o -z "$LOCAL" ]; then
echo QMAILDUID, NOFILESGID, MAXSMTPD, or LOCAL is unset in
echo /var/qmail/supervise/qmail-smtpd/run
exit 1
fi

if [ ! -f /var/qmail/control/rcpthosts ]; then
echo "No /var/qmail/control/rcpthosts!"
echo "Refusing to start SMTP listener because it'll create an open relay"
exit 1
fi

exec /usr/local/bin/softlimit -m 2000000 \
/usr/local/bin/tcpserver -v -R -l "$LOCAL" -x /etc/tcp.smtp.cdb -c "$MAXSMTPD" \
-u "$QMAILDUID" -g "$NOFILESGID" 0 smtp /var/qmail/bin/qmail-smtpd 2>&1

Much obliged !

Looks like everything is good. My advice would be to look for either a firewall that is blocking your connection, or a DNS problem along the way. Maybe you don't have a MX record for this domain? Maybe you're using a 3rd party DNS that isn't setup properly? Hard for me to help you with DNS because I don't know your true domain or IP. If you're not sure about your firewall setup, try running "iptables -L" and see what comes up. If you get a bunch of "ACCEPT" statements, then you're probably ok. Another possibility may be your networking appliance. Maybe it's not setup to allow port 25 traffic?

Just throwing out some ideas.