On Thu, Jun 25, 2015 at 08:11:45AM -0400, sashk wrote:
> Is there a way for me to instruct postfix not to attempt delivery to
> second MX host, if first attempt failed?
That would be wrong.
> According to the Google Apps support, it's exactly what causes the
> temporarily ban.
Nonsense. Trying the next MX host is what every MTA should do when
the first MX host returns a 4XX code:
https://tools.ietf.org/html/rfc5321#section-5.1
https://tools.ietf.org/html/rfc5321#page-70
When the lookup succeeds, the mapping can result in a list
of alternative delivery addresses rather than a single
address, because of multiple MX records, multihoming, or
both. To provide reliable mail transmission, the SMTP client
MUST be able to try (and retry) each of the relevant addresses
in this list in order, until a delivery attempt succeeds.
However, there MAY also be a configurable limit on the number
of alternate addresses that can be tried. In any case, the
SMTP client SHOULD try at least two addresses.
> Well, google says otherwise. They say, there was two attempts to
> connect within the second, and they're banning me for that.
What evidence do you have for that? The error messages are about
message arrival rate for the same user. I am quite familiar with
these, and they are not caused by a small number of closely spaced
messages. Rather this symptom happens when a user quickly receives
a large number of messages due to a flood of mail coming in.
--
Viktor.
