Misconfig Allows Emails to be Delivered to Users Who’ve Clicked Spam

  • 1
  • March 6, 2016



3 out of 6 servers were ignoring FBL (feedback loop) data, allowing users who’ve clicked spam to keep getting emails.


Customer believes these issues had been around for months.  Identified by Email Copilot as soon a enough data was available to verify the condition.

Sending 250M emails per month

Anonymous | Email Marketing Specialist

“We always knew we were getting blocked heavily at Yahoo! and AOL, but never really knew why.  We’d nearly accepted this as ‘how it’s going to be’ for us.  The folks at Email Copilot helped me realize we’ve had a very serious long-term configuration error.  Once resolved the AOL and Yahoo! blocks dropped to almost zero.”


Our technology in action:

What we do that others cannot…

Direct access to all raw email-level details.

Because we have direct access to your raw ESP + ISP data, our system categorizes every email down to the user and original email sent. With this, we’re able to easily see anomalies like this where users are getting emails they shouldn’t.

Our deliverability and data science teams at work

We saw heavy spikes in deferrals and blocks at Yahoo! (TS-01, TS-02) as well as AOL (CON-B1). Because we have complete flexibility to dig into raw data, we were able to quickly slice and dice the data to find the culprit.


Clear issues at AOL, resolved.

Within the following images, you can clearly see how quickly and dramatically the problems at AOL were eliminated.

Configuration fixes were implemented on the 7th and 8th, and AOL responded in dramatically positive fashion on the 9th.

Pre-fix data points:

  • 400,000 emails per day sent to AOL
  • Deferral rate at AOL averages 92%
  • Bounce rate at AOL peaks at 34%

Post-fix data points:

  • Same volume of emails to AOL
  • Deferral rate at 2.6%
  • Bounce rate at 1.4%

Another view showing AOL CON-B1 deferrals disappear to nearly zero.

An additional bonus:  Server Errors (bounces) dropping dramatically as well.

Clear issues at Yahoo!, resolved.

The above fix worked for AOL, but a further set of adjustments needed to be made to make Yahoo! happy.

Configuration fixes were implemented on the 29th, and Yahoo! responded with the same positive fashion in just a couple days.

Pre-fix data points:

  • 1,100,000 emails per day sent to Yahoo!
  • Deferral rate at Yahoo! averages 81%
  • Bounce rate at Yahoo! peaks at 47%

Post-fix data points:

  • Same volume of emails to Yahoo!
  • Deferral rate at 2.9%
  • Bounce rate at 0.1%

Another view showing Yahoo! TS-01 and TS-02 deferrals disappear to nearly zero.

An additional bonus:  Timeouts due to deferrals (bounces) dropping dramatically as well.