Hello,
I just had a situation where the sending postfix
(me) uses greylisting, and the receiving postfix
is using address_verify_sender.
The greylisting generates a 450 response to
the address_verify_sender query triggered by
the initial email. The receiving postfix
appears to be caching this as a failure,
and not retrying the verify sender for some time.
During that period the sending postfix retries
mail delivery, but continues to get a 450
from the receiver until address_verify_negative_refresh_time
runs out.
I believe that address_verify_sender should not cache
4xx responses as failures. Then when the sender retries
the receiver will also retry it's address_verify_sender,
the greylisting should allow the query, and the mail
would then be delivered. (This assumes that the
greylisting is configured on the sending site
in a fashion that would not
block a site with the same retry policies as the
sending site. This seems a safe assumption.)
Being the sender, I do not have a postfix version
number for verify.
Regards,
Karl <kop AT meme DOT com>
Free Software: "You don't pay back, you pay forward."
-- Robert A. Heinlein
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