Major ESP Not Adjusting for “450 Too Many Connections” Deferrals

  • 0
  • November 24, 2015

CASE STUDY

Problem

Major ESP was receiving 1M deferrals per week for a single k12.ca.us domain, and not backing off on “450 Too Many Connections” requests.

Solution

Email Copilot’s alerting system identified this very specific deferral issue within 3 hours and the ESP was able to resolve the problem within the day.

A major ESP with hundreds of thousands of customers

Anonymous | Deliverability Engineer

“There did indeed appear to be quite a large number of deferrals for messages to that domain. We’ve made some changes with our servers that seem to have lessened the effects of rate-throttling.  Thanks!”

HOW WE SOLVED IT SO QUICKLY

Our technology in action:

What we do that others cannot…

Direct access to all raw email-level details.

Because we have direct access to the raw ESP/MTA + ISP data, our system is able to identify anomalies like this one in real-time.  Even anomalies with this granular-level of issue (emails from one customer, to one domain, high deferrals of the type “Too Many Connections”) are easy for Email Copilot to spot.

Incredible visibility into the data

Simply clicking on the deferral alert provided the necessary context to point at the problem.  No more digging into log files to figure out what’s actually going on.  Point.  Click.  Answer.

WE LET THE DATA DO THE TALKING

Beating up a K-12 server, resolved!

This data shows how heavily the receiving mail server was getting hit, drowning under too many re-tries.  The vast majority of the error messages were “450 Too many connections from your IP (rate controlled)”

A quick fix by the ESP resolved this problem and email flow returned to normal.

Pre-fix data points:

  • 1st 5 hours of data shown
  • If unchecked, would result in 1M emails deferred to this single k12.ca.us domain per week
  • Average of 250 deferrals for each email message sent
  • Emails coming from a customer that provides services to California K-12 school systems

Post-fix data points:

  • No change in volume from customer
  • Deferrals reduced to normal levels
  • Emails accepted by the receiving server again
  • Customer ecstatic that their ESP resolved this so quickly

Comments

comments