Nico Erfurth <masta@???> writes:
>> are expected to work this way. If no IP connection can be made to the
>> first MX, other MXes should be tried. As a result, SMTP mail delivery
>> is extremely robust, and certainly you don't want to change this.
>
> The IP connection was established if you get the 5xx response.
Sorry, I thought Suresh was talking about blocking at the IP level.
Suresh, please accept my apologies.
> Sorry but what you describe is a usual spammer-practice. The
> connection was rejected on SMTP-Level, not IP-Level.
There is no reliable way to reject connections on the SMTP level. And
to me, it's questionable why blocking at the IP and SMTP levels should
have wildly different semantics ("Try next MX, please." vs. "I don't
know what domain you were looking for at this server, but it does not
exist. Go way, and bounce the message.").
Not that I would say that it has to be one way or the other, but I
can't ignore the fact that the behavior of real SMTP clients and
servers is far from being consistent in this area.
