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What Factors Can Impact Email Message Delivery Times?

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by: Jeff Dellapina (@IBMforMarketing)
19 August 2013

When we hit “send” on an email to a friend or family member, we’re used to the message being delivered within a minute or so. In the marketing world, where the number of email recipients can number in the thousands – or even millions – the process can take longer. So, what factors can impact the length of time between when a message is sent and when the email arrives in a recipient’s inbox?

Email delivery delays can occur for many different reasons. Before we discuss these reasons, let’s start by talking about the process of how an email marketing message is delivered.

Typically, a marketer will create a mailing template and assign that template to a list. In the case of Silverpop Engage, our platform builds the mailing, checks the suppression list and then hands the messages off to the sending server – a.k.a. our client’s IP Address. The server continues to deliver the message until it is accepted, bounced or times out. (A message will time out if the receiving server never accepts the message.)

In a perfect world, every ISP would take every message within the first few minutes. And in fact, most email gets delivered in a couple of minutes. But depending on the size of the mailing (as well as your marketing platform’s custom settings), some messages may take hours or even days to get delivered.

The main reason for delivery delays is ISP throttling. Sometimes an ISP will take all your mail in just a few minutes and then take its time handing out those messages to the various recipients. Other times, the messages are still on the server hours after the send as your marketing platform waits for the receiving server to take and deliver the mail.

The two primary factors that impact how an ISP throttles emails — and thus how long it takes for your messages to get delivered — are authentication and IP reputation/recipient behavior:


Incorrect or missing DNS records will reduce the rate that an ISP will accept messages. Since it takes longer for the receiving server to validate the messages, those emails get delivered at a slower rate —or not at all.

IP Reputation/Recipient Behavior

ISPs will limit the amount of messages into their network based on sender and recipient behavior. If you sent to too many bad email addresses, for example, this poor sender behavior might result in the ISP reducing the amount of mail (throttle or rate limit) it accepted. Sending to very old addresses will also impose rate limits.

Recipient behavior is what the recipient does with the message once it’s received. If the recipient opens/clicks on the mailing or moves mail from the bulk folder to the inbox, that’s considered a good behavior that would increase the email volume entering the network. Deleting the mail without reading or clicking on the abuse button would be a bad behavior that would decrease the volume of email entering the network.

Speeding Up Your Delivery Time

If you want to improve your delivery rate, focus on improving your IP reputation. You can enhance your IP reputation by sending to the active openers/clickers in your database, which reduces bad mailbox issues, abuse complaint issues and bounces. Sending to old inactive addresses generates high abuse complaints, spam trap hits and reduced opens, which makes your mailings look less important.

Working more behavior-driven emails into your messaging mix will also help. Since these emails are triggered by the actions of the recipient, you’re mailing to “audiences of one,” so not only are the message more relevant, but you don’t have to worry about the throttling issues that you have with a mass broadcast mailing.

Related Blogs:

1)  “New Gmail Tabs: Big Yawn or Zombie Apocalypse for Marketing?

2) “Pssst, Do You Have Any Warmed IP Addresses?

3) “Yahoo Is Releasing Inactive Yahoo IDs: What It Means for Marketers


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