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Re: [ietf-smtp] [Emailcore] Status of Greylisting (i'd wish MessageID were part of SMTP prologue)

2022-01-06 18:23:58
It appears that Steffen Nurpmeso  <steffen(_at_)sdaoden(_dot_)eu> said:
This is interesting, for example the Firefox browser i use only
can manage one password for all the IETF mailing-lists i am
subscribed too (iirc, many many months, but it tried to auto-fill
a false one now, and i definetely recall having problems with
password auto-fill for mailing-list subscriptions), so
auto-filling the password just does not work.

I believe you, but that has nothing whatsoever to do with SMTP or
the way that mail works.

These are interesting numbers far beyond mine, thank you!  (It
surely will increase now that i post on @ietf.org, as always.)
Yes /24, not /8.  Really very interesting that /24 is of so much
use even today.  Many sites use multiple "deferred" until a retry
is accepted, and your "one month" white listing is also a number
quite large i think.

It might as well be forever.  The only point of greylisting is
to see if an MTA follows the spec well enough to retry.  Once
you've seen a retry, greylisting is of no further use for that
source.  The only reason I time out after a month is to keep
the local whitelist database from getting too big.

I find it interesting that such simple greylisting that cannot
even correctly identify a specific message seems so useful still.

But identifying the specific message is not important. How often does
a spambot send two different messages with the same envelope in a
time gap that makes it look like a retry? Basically, never.

I have tried a version of greylisting that did the retry after DATA
and kept a hash of the message. I found that a certain number of
systems regenerate the retried message in a form that is not quite the
same, e.g., different timestamps. The hashes don't match and the
retries always failed.

R's,
John

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