Throttling K-12 Email Lists

Throttling K-12 Email Lists


What is email throttling?

Email throttling in simple terms is Internet Service Providers (ISPs) limiting/controlling the intake of emails from a sender if it crosses a certain threshold. You may be blocked by an ISP when you send too many emails at one time. (

Changing the format of our Education Marketing Lists

Around 2013, a year after K12 Data went to market, we started hearing about email delivery issues. My first reaction, as usual, is to have a meeting with our Head of Data Operations to ferret out any quality issues in our accurate education email lists. Maybe the team botched an upload or missed a data verification cycle, no idea. So I spoke with a few customers to see if I could pinpoint the issue. It wasn’t the quality of our education database it was the delivery. If you go back a decade or even two you would remember that Bulk Email purchasing and delivery was rampant. Customers would regularly purchase 100k teacher contact email lists and blast away. It was the wild west and this type of blanket e-marketing was the norm for many companies. The problem was that the ESPs (email service providers) started having issues with their emails being blocked after delivering to the same mailboxes in bulk - all at once. And that was it. The common conversation was that “my emails just fell off a cliff about 1/5th of the way into my campaign to Broward Schools”.

The Basal Level Remedy 

Here it is - our education email lists, which are delivered in an automated fashion, on export, were sorted by the institution name and generally next by zip code. So what was happening was that our clients were blasting 10k emails to teachers in most of the same districts’ schools. The incoming mail blanketed inboxes almost simultaneously and that immediately triggered spam filters and stopped all incoming email in its tracks. If you have ever used Gmail or Outlook to BCC blast to your house file and you got locked out of using your mailbox for 24hrs then you are familiar with the concept (rule). If you are still sending through Outlook or Gmail then I encourage you to purchase your data from MDR or Agile (pull pin with teeth and toss grenade over). Because the ensuing conversations about how “my file had a 30% bounce rate before being shut down” will be the new norm from the not so happy new customers. The basal level fix was that I asked our developer to have all lists sorted by Last Name. The next step was to tell our clients that were say sending Principal Email Lists by the thousands to break the files into smaller chunks of say 3-5k when loading into the email delivery platform. Then send in these same smaller bites. The change was it and things went smooth immediately after. 

Check with your ESP when you are ready to launch your next Teacher Email Marketing List to all the US schools and make certain you are throttling your sends or your deployment company has the service built into their platform. I recently had this conversation with ClickBack ( and they do.

Thank you,

Charlie Isham

K12 Data Inc.

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