Delivery Speed & Send Delays Follow

Before we dive into the intricacies of what can cause delays, we'll cover some basics of how our email delivery works.

System delivery speed

The email marketing system has a range of different IP addresses - lots of them. When you send an email, your contact list will be split over several IP addresses for delivery.

Our IP addresses work similar to a queue in a grocery store - first person at the check out gets served before the others in line. Back to the IPs, this translates to first emails in the queue are delivered first.

In an ideal world, you'd be the only person in the queue and your emails would be sent out at a rate of 50/s. But in reality, our IP addresses are shared among all our customers. So at any particular time that you send an email, it's likely that there are already some emails in the queue ahead of you.

How we protect your deliverability

Now, you might be thinking that the email delivery should be really fast if we're splitting your emails across all our IP addresses. And you're right. But that's not how we split up your email send.

So why don't we do it that way?

Every now and then we might get a customer who accidentally (or sometimes maliciously) gets our IPs blocked. By separating our customers onto different IP ranges we minimize the potential issues that any one customer can cause.

But wait...there's more

Here's when we get into the more complicated details around email delays.

Now, the queuing process that we spoke about earlier processes quite quickly, with the system processing about 50 emails per second (variable). But every now and then we do see extremely large volumes of emails through the system, which is when this processing rate might slow down.

However, there are factors external to the email marketing system which can also affect the delivery speed of your emails, like the rate at which your contact's domain provider (e.g. Gmail, yahoo, Hotmail) accepts the emails.

Some domain providers only allow emails to be delivered at a certain speed (some slower than others), which can also affect the delivery rate of your emails.

What should you do if you experience send delays?

As you can see, delivery speed is a complex interaction of many variables. So how should you go about troubleshooting send delays? I've included a few ideas below to get you started.

Internal Delays

If the email delays you are experiencing are to internal email addresses (like a colleague's email address, or your own), you might like to try the following troubleshooting tips.

  1. Send the email to a personal non-work email address

    Try sending the email to your own personal email address (like Gmail, Yahoo, Hotmail etc.) to see if there is also a delay to that address.

    If there is a delay, the issue might be that there is a large number of emails being sent through the system at the same time, and your emails will be processed once the queue ahead of them has cleared.

    If there isn't a delay, the issue might be isolated to your work email address, in which case you can continue the troubleshooting steps below.

  2. Change the sender address of your email

    Sometimes your work email won't like that there is an incoming email from a third party which is also using a work email address. We therefore recommend editing your email, clicking the Details button in the top right corner, and changing the From Address field to a personal email address (like Gmail). You can then re-test the email by sending the email to your work email address.


  3. Contact your IT team

    The next step is to contact your IT team with the results of the above two troubleshooting tasks. Let them know you are experiencing delays to your work email from your email marketing product, so they can investigate to resolve the issue. You also might want to send them the information below, which might help them troubleshoot further.

    The IP address ranges which the email marketing system uses for sending:

    Other potentially useful information:

    The return-path is
    All mail originates from a server with a hostname that ends in

External Delays

Have you become aware of send delays to your subscriber database? You might like to try some of the troubleshooting steps below.

  1. Take note of the domains that are experiencing the delays

    Are the recipients who experienced the delays all using Gmail accounts? Or maybe they are all from the same company? Take note of the domain they are using, then check your reports to see how many other people are using that same domain.

    If there are large volumes on the domain which is experiencing delays, it is likely that the domain provider is controlling how many emails can be delivered at one time. In this instance, your emails will likely be delivered to the recipient when their domain provider clears the incoming queue.


  2. Are the delays repetitive or a one-off occurrence?

    If the delays are repetitive this again points to the domain provider limiting the amount of emails that can be delivered at once.

    If the delay seems to be a one-off occurrence, it might be because there was a queue of emails ahead of yours at the time you hit the send button. In this instance your emails will be delivered when the queue has cleared.

  3. Can you replicate the delay during testing?

    The next step would be to try to send yourself a copy of the email, to see if you can replicate the delay.

    If you are sending a test, it is best to send to the same email domain as your recipient which is experiencing the delays. For example, if your recipient is using a Gmail account, send the test email to your own Gmail account.

    If you don't have an email account with the same domain that's okay. Just run the test to the email account that you use the most.

    Take note of the results of your test (whether there was a delay or not - if there was a delay, how long was it?)

  4. Submit a request to our customer success team

    If you think that this is an ongoing or widespread problem, please submit a request to our customer success team who can investigate further.

    We will need the following information to investigate:

    - Your account ID
    - The date and time of the original email send
    - The name of the email message
    - The email addresses of those recipients who have informed you of the delay
    - The results of any troubleshooting / investigations you have done
    - The date and time of any emails you sent to test the issue
    - The results of the test (e.g. delay time experienced)

    Once we have this information we can take a look at the send logs and determine if there was a queue at the time of sending which caused this, or whether there are any other problems.

    Please note that we will only be able to investigate up to a point - if we think the delay is on the recipients end (e.g. we can't find any problems or queues on our end) we will let you know and it will be up to you or the recipient to troubleshoot the issue with their domain provider.
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