On 2021-04-21 13:34, John Levine via mailop wrote:
It appears that Peter Nicolai Mathias Hansteen via mailop<pe...@bsdly.net>
said:
Greylisting implementations tend to expect retries to come from the same IP
address as the original one. Some of us are still quite cross that
the writers-of-RFCs did not care to make that a MUST requirement (see [1] for
my grumble on that from a while back).
SMTP was defined in the late 1970s and we didn't invent greylisting
until about 2003. I don't think you can blame them for not being
clairvoyant.
I find that fuzzing the IP addresses to anything in the same ipv4 /24
or ipv6 /64 handles most of the different IP retries without letting
any more spam through.
I also just ignore the IP completely for mail marked as SPF:PASS. A
quick and easy way to let the sender define what IPs they use and I
don't need to worry about the outbound IP changing.
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