On Fri, 17 Sep 1999, Russell Nelson wrote:
> Because you claimed that it was speaking SMTP. Upon examination, it
> isn't. Your MX records are false. Why should I send your server any
> mail at all, since it may not be the right server at all?
1. The host is dead => it does not send any datagrams =>
it does not speak SMTP.
2. The host is alive but no process listens on SMTP port => it refuses
TCP connections => it does not speak SMTP.
3. The host is alive, some process listens on SMTP port but something
gets screwed up when a connection is open, and the connection is closed
immediately (e.g. qmail-smtpd binary is corrupted and dies immediately)
=> it does not say SMTP hello => it does not speak SMTP.
Summary: the server fails to speak SMTP in all cases.
Ergo, if the server is listed as an MX record for some domain name, "I
claimed it was speaking SMTP but upon examination, it isn't, therefore MX
records are false." In ALL cases 1, 2, and 3. Why does qmail fall back to
other MXes in cases 1 and 2 but not in case 3? Why does it fall back at
all? It should always ignore the other MXes because the records are
always incorrect according to your reasoning!?
Let's have a private network having two gateways: a primary one and a
backup one. The gateways accept e-mail traffic from the Internet and
forward messages to some system running on the private network (that is
not visible to the outer world). Any gateway is able to do this but the
primary one is listed as the first MX because its performance is better.
If the primary gateway breaks, the messages from qmail will be delivered
through the backup one in failure cases 1 and 2 but not in case 3. This is
strange, isn't it? Why is case 3 special? Is there anything wrong with
this setup? If yes, enlighten me, please. :)
BTW: I have omitted a case when the server accepts connections, starts
SMTP conversations but it always (as far as the client knows) dies in
the middle of the conversation. It depends on Russell's definition of
"speaking SMTP" whether such a host speaks SMTP or not.
Your Advocatus Diaboli, :)
--Pavel Kankovsky aka Peak [ Boycott Microsoft--http://www.vcnet.com/bms ]
"Resistance is futile. Open your source code and prepare for assimilation."
