On Thu, 28 Jun 2018 19:25:12 +0000, Michael Wise via mailop
<[email protected]> wrote:
>If you start to see 4xx deferrals (esp. 3113, 3114, 3115, 3150,
) from the
>Hotmail/Outlook/et al data centers, you should know that the IP has been
>throttled, and one would be well advised, given that situation, to STOP all
>sending until at least the top of the hour, plus a few minutes. And if the
>deferrals continue with THAT traffic, it is strongly suggested that one hold
>off on any sending from that IP for at least 24 hours. Bottom line is, right
>now, if you start seeing 4xx deferrals from HotMail on a given IP, you
>should stop sending immediately if you at all possibly can as it may affect
>the IPs reputation. But in general, if when you connect to a given mail
>server, all you are seeing is deferrals, you should 1) notice, and 2) back
>off.
A client recently notified us that he was seeing 100% deferral from Hotmail
(and all the associated domains), and sought remediation advice.
Remembering the above, I put in a throttle program that would cease sending
for 4,000 seconds whenever more than 5% deferrals were seen in any given
five-minute period when at least 20 delivery attempts were made.
This did not remedy the situation, so we drained that queue into an unused IP
and warmed it up gently; the traffic was then accepted without incident.
After a couple days inactivity I began to trickle traffic back into the
original IP, where it was also accepted without issue. I have configured
their system for "minimum surprise".
>And you should do some navel gazing to make sure those deferrals were not
>happening for an as-of-yet un-noticed cause.
Looking at the sending history of this client (verified opt-in, reasonably
engaged, no sending to stale accounts, modest but bursty daily volume) my best
conjecture is that their earlier configuration allowed a rather large inrush
when a campaign began, and that recently this began to be considered abusive.
mdr
--
The Duckage Is Feep.
-- Vaul Pixie
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