I have a customer who is running Qmail 1.03 server (running on Linux).
The Qmail server is located in a DMZ behind a firewall. All incoming mail
is proxied through from the internet to the Qmail server in the DMZ which
then relays it in to an Exchange server on the internal network. All
outgoing mail is relayed from the Exchange server to the Qmail server on the
DMZ which then delivers it.
The problem that they are having is that when the Qmail server tries to
deliver the email the following happens....
Qmail server does a lookup of the relevant MX/DNS records for the mail
domain.
Qmail makes a SMTP connection to the first MX entry for the mail domain.
- In reality the Qmail server is making a SMTP connection through the
default gateway (the firewall). As it is a proxy based firewall, it makes a
SMTP connection to the first MX entry of the mail domain on behalf of the
Qmail server.
The server listed as the first MX entry for the mail domain is not currently
alive.
The SMTP connection from the firewall to the remote SMTP server 'fails'.
The firewall drops the connection that the Qmail server has made to it.
This connection is 'lost'.
Qmail says 'I had a connection but it was lost' and so flags that IP address
to try later.
Qmail tries that IP address later, again and again and again.
Qmail never steps to the next MX entry for the mail domain.
The mail doesn't get through!
I have talked to the firewall manufacturer about this, but they say that
there is nothing they
can do.
Does anyone have any ideas or ways to get around this?
Thanks,
Karl Lellman
Systems Consultant
Extranet Technologies Limited
PO Box 47-808, Auckland, New Zealand
Mobile +64 25 771188, Fax +64 9 3094631
e-mail: [EMAIL PROTECTED]
