On Wed, 30 Aug 2006, Alex van den Bogaerdt wrote:
This could very well be a problem on the MX itself. It is not unreasonable to
try another mail exchanger that may be able to receive the message. In fact,
RFC974 has this to say:
"Implementors are encouraged to write mailers so that they
try the MXs in order until one of the MXs accepts the message, or all
the MXs have been tried."
If this statement is revoked in a later update, I'm unaware of it (pointers
welcome!)
I believe that common implementations try the other MXs immediately.
I think the question is what should prevail, the 4xx status or the 5xx status.
The 5xx status, because it's a definite result, and rejecting the message
following an immediate fallback to the fallback MX was the behaviour
(erroneously) intended by the destination site.
Tony.
--
f.a.n.finch <dot(_at_)dotat(_dot_)at> http://dotat.at/
FISHER: WEST OR NORTHWEST 4 OR 5 BECOMING VARIABLE 3 OR 4. FAIR. MODERATE OR
GOOD.