On Wed, 13 Aug 2025 19:33:40 +0200, "Peter N. M. Hansteen via mailop"
<mailop@mailop.org> wrote:
>The best condensate is along the lines of, when a greylisted host
>tries to deliver mail to a known-bad address, that host is trapped
>initially for 24 hours. During that period, any further traffic from
>that host is "stuttered at", with our side answering one byte per second
>by default (but tuneable to 1 byte every 10 seconds).
>
>This means that each delivery attempt from a trapped host typically takes
>between 300 and 700 seconds, with a few *extreme* outliers.
After an initial email to a "sudden death" spamtrap here, the IP is put on the
no-connect list for 24 hours. On a second offense, it is now three days. Then
six days, then eleven days.
Recently an average day will see 52 first-time offenders, and several hundred
connection attempts from blocked IPs, often including retries from
just-blocked sources. This morning the logs showed that on the previous day
we had 67 connection attempts from IPs which had offended at least twice. Two
of those IPs belong to Google.
Apart from the occasional "Hey, what's with this '530 4.7.0 Connection
refused' that Gmail is telling me about?" and an occasional Sendgrid mailing
list message that has to retry from a different IP, it's been doing us well
for a little over 20 years now.
mdr
--
Those who can make you believe absurdities
can make you commit atrocities.
-- Voltaire
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