Prime Sending Times: Using Prime Numbers to Improve Delivery

Todd Herr
Oct. 24, 2016 by Todd Herr

Prime Sending Times: Prime numbers floating from clock to envelope

Determining Prime Sending Times with Prime Numbers

You may remember learning about prime numbers in middle or high school math class. These of course, are numbers that only divide by themselves or one. You may also remember thinking, “I’ll never need to know these”. However, I’m here to tell you that they can be useful to you in ways that might improve your email delivery.

Recently, I was helping one of our clients deal with a problem where most, but not all, of their batch send to a large mailbox provider was getting through on the first try. The rest was getting through eventually (within minutes), but the client really wanted it all sent on the first run. We have a contact at the mailbox provider, so I reached out to him to see about a solution. Over the course of the conversation, he said something that stuck with me:

“Our inbound traffic volume at 8:03 is ten times what it is at 8:43.”

The reason for this, is that there are lots of bulk senders who have regularly scheduled sends during the day. Of those sends, nearly all of them kick off at the top of the hour. Mailbox providers, especially large ones, have the capacity to deal with large spikes in traffic. However, even the largest providers have finite resources, and if everyone and their brother makes demands on them at the same time, some messages are going to have to wait.

This Is Where Prime Numbers Come In

Unless you absolutely have to send your mail at the same time as everyone else, you might find that your delivery times are improved if you pick a time for your regular sends that is not right on the hour, quarter hour, or half hour. Instead, pick a number from the list below (all prime numbers) as the time past the hour for your send, and see if your delivery doesn’t improve a bit:

1, 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59

With the exception of 5, most of these numbers are probably not ones that people would use for scheduling purposes. We’re most likely to use the numbers we remember from the clock face, rather than all the ones in between. It’s likely that if you send your regular mailing at, oh, 8:23 instead of 8:00, you may find that you’ve got more capacity available to you at the destination domains. As a result, your queues may clear much faster. Happy Sending!

-Todd

ps: Any additional thoughts about prime sending times? We want to hear – comment below or Tweet us!

2 Comments

  • Thank You. That’s a smart insight.

  • Hey Ankur,

    Glad you found this trick useful!

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