Understand Smart Sending in Klaviyo

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You will learn

Learn about Smart Sending, which allows you to limit the number of emails or SMS someone can received within a set period of time. 

This is a good way to prevent your subscribers from receiving too many messages at once if you have many active flows and campaigns.

About Smart Sending

When an email or SMS message has Smart Sending enabled, Klaviyo will automatically check to see if that profile has received a message from you within your account's Smart Sending period before it sends. If this profile has received another message from you too recently, they will be skipped from receiving the current message.

Keep the following in mind when using Smart Sending: 

  • Emails and SMS messages have separate Smart Sending windows
    • Email default: 16 hours
    • SMS default: 24 hours
  • You can change the Smart Sending windows at any time
  • Messages skipped due to Smart Sending are not rescheduled automatically
    • For information on resending emails, read How to resend emails in Klaviyo
    • Currently, it’s not possible to resend a text message to someone who was skipped due to Smart Sending except by doing so manually. 
  • Updating the smart sending window does not retroactively affect recipients
    • Example: If you send an email campaign and then change the email Smart Sending window from 16 to 10 hours, anyone who received that campaign will be skipped from emails until the full 16 hours pass

Change the Smart Sending timeframe

As mentioned the Smart Sending timeframe for email and SMS are separate, so you can adjust one without affecting the other. 

Email Smart Sending window

By default, the email Smart Sending window is 16 hours. 

  1. Navigate to your organization name in the bottom left corner of your screen.
  2. Click Settings.
  3. Select Email.
  4. Update the number of hours under Smart Sending Period.
    Smart Sending timeframe in the email settings page
  5. Check the box to Ignore transactional messages if you send transactional emails.
    • In almost all cases, Smart Sending should remain disabled for transactional emails, as these are messages that customers anticipate receiving and search for in their inboxes.

SMS Smart Sending window

By default, the SMS Smart Sending window is 24 hours. 

  1. Navigate to your organization name in the bottom left corner of your screen.
  2. Click Settings.
  3. Select SMS.
  4. Edit your Smart Sending period within the SMS Sending Settings area.

SMS sending settings, including the default Smart Sending window

Disable Smart Sending for a message


Smart Sending is enabled by default for all campaigns. You can choose to disable Smart Sending on a per-campaign basis. We recommend keeping Smart Sending turned on for most, if not all, marketing emails.

In step 1 of the campaign, toggle off the option to: 

  • Email: Skip recently emailed profiles.
  • SMS: Skip recently messaged profiles.

Smart Sending in the recipient's section for a campaign



Smart Sending is not enabled by default for flow messages. You can choose to enable Smart Sending for an individual flow message.

  1. Click on an individual flow message.
  2. Click Smart Sending under Settings on the left-hand side.
  3. Toggle on Smart Sending.

Flow sidebar when Smart Sending is turned on


Smart Sending and A/B testing

A/B tests that receive no results due to Smart Sending are automatically cancelled. This means that everyone in the test pool for your A/B test campaign got skipped because they received another message too recently. If you receive an in-app notification like the one below, your A/B test has been canceled and you need to resend your campaign to reach your recipients. 

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