"Ng, Kenneth (US)" wrote:
>
> The question I have in all this, why is it that Exchange does not retry
> sending the email with the other MX entries? I understand that Exchange
> sees a connection completed, and then a connection broken. At that point
> why doesn't Exchange try one of the higher MX entries?
Exchange does not see the connection broken. The entire message gets
queued to the firewall so as far as Exchange is concerned the message
has been delivered to the lowest MX value. When the firewall fails at
delivery, no error codes are returned to Exchange so it never knows any
better.
IMHO Exchange is fine as any other mail system breaks the same way (I've
seen this will Sendmail, Notes and a number of 3rd party SMTP gateways
as well). The problem is that the functionality of the SMTP security
server only lends itself to inbound use.
> I have a Sun running
> sendmail behind a Raptor firewall and it sends email out to the internet
> just fine.
Completely different animal. Raptor will do an MX lookup to ensure final
delivery. If it can not, it will kick back a message undeliverable to
Sendmail.
Cheers,
Chris
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