Klaviyo Smart Sending: when to leave it on and when to turn it off

This is for Shopify founders who sent a campaign, looked at the numbers and asked, "why didn't everyone get my email?" Most of the time, that's Smart Sending doing exactly what it was built to do.

What is Klaviyo Smart Sending?

Per Klaviyo's help center, Smart Sending limits how many emails, SMS messages or push notifications someone can receive in a set period. If a person already got a message inside the window, the next one skips them.

Here's what Klaviyo's page says about how it works:

• Default windows: 16 hours for email, 24 hours for SMS, 24 hours for push.
• Separate channels: Email and SMS are managed independently and don't affect each other. An email in the morning doesn't block a text that afternoon.
• Changing the window: You can change it in your account's sending settings, for email, SMS or push. Changes don't take effect right away and don't apply to people retroactively.
• Transactional messages: They're never skipped, and getting one doesn't cause someone to be skipped later.

How does Smart Sending work in campaigns and flows?

Campaigns. Smart Sending is on by default. You can turn it off per campaign in the message's settings, under the Recipients step of the builder. Klaviyo recommends keeping it on for most, if not all, marketing emails.

Flows. Klaviyo says it's enabled on flow messages in many pre-built flows. You can turn it off for an individual flow message in that message's settings: for email, clear "Skip recently emailed profiles."

A few details that trip people up:

• The timer starts for everyone Klaviyo tried to deliver to, including failed deliveries. It doesn't start for people who were skipped.
• Turning Smart Sending off for a message still resets the timer for everyone that message went to.
• Klaviyo says A/B tests that get no results because of Smart Sending are cancelled automatically, and you'd have to resend.
• For SMS, skipping is based on the phone number, so profiles that share a number can skip each other.

Why didn't everyone get my email?

Usually because they got something else from you inside the window. Flows send all day. Your welcome series, abandoned cart and post-purchase emails are going out while you're writing tomorrow's campaign.

Say a few hundred people get a flow email at 9pm and your campaign goes out at 10am the next day. That's 13 hours, inside the 16-hour window, so Smart Sending skips them. That's a made-up example, but it's the most common reason a send looks smaller than the segment.

That's fine on a normal day. Someone who got a cart reminder last night doesn't need your Tuesday campaign this morning. The problem is when the campaign is the one email everybody needed.

When I'd leave Klaviyo Smart Sending on

For most campaigns, I'd leave it on. My normal cadence is about one campaign every other day, with consecutive sends only for major promos. At that pace, Smart Sending mostly protects people from a campaign landing on top of a flow email.

It's a guardrail, not a strategy. It doesn't decide who should hear from you more often. Segments do that. I cover how to split frequency by segment in how many emails per week to send.

When I'd turn Smart Sending off

Here are the sends where I'd turn it off on purpose, because missing part of the list costs more than one extra email does.

1. Your automations. This is the one most founders never check. Flow emails are the critical reminders: abandoned checkout, abandoned cart, back in stock, reorder. You don't want someone missing their checkout reminder because they happened to get a campaign that morning. At a haircare brand I work with, Smart Sending was on for the abandoned checkout emails, and a chunk of people simply never got their reminders. That's revenue lost to a setting nobody remembered turning on. Go through your flow messages and clear "Skip recently emailed profiles" on the ones that matter.

2. Restock announcements. When something sells out, the restock email is your biggest send of the month. At a snack brand doing about $650K a month, "We're back baby!" made $48,771 from 30,498 people, the brand's best campaign ever. Its back-in-stock emails earn about 1.7x its average per person. You don't want part of that list skipped because they got a post-purchase email last night.

3. Last-chance deadline sends. A "this ends tonight" email only works if it lands before the deadline. Skipped people aren't rescheduled, per Klaviyo, so a skip here means they never hear about it. At a snack brand, "Your special discount ends at Midnight!" made $11,560, about 7.2x that brand's typical email.

4. Launch days. A new product email is news, and people want to hear it the day it drops. In my subject line data, launch-style subject lines earned about 1.26x the same brand's typical revenue per email.

5. BFCM days with more than one send. Black Friday is Nov 27 and Cyber Monday is Nov 30 this year. If you've planned a morning send and an evening reminder on the same day, Smart Sending on the second one will skip the people who got the first. I lay out the full send plan in my BFCM email strategy.

On those heavy send days, I don't change the flows themselves. They run exactly as they always do. The point of having Smart Sending off is that nothing gets skipped: campaigns land, flow reminders land, and nobody falls through a 16-hour crack on the biggest revenue day of the year.

Won't turning it off make people unsubscribe?

Probably less than you'd guess. Across 4 consumable brands I work with, 3 of the 4 saw no rise in unsubscribes when they sent more. That's a small sample, so I don't treat it as a rule. I go through the numbers in does sending more emails increase unsubscribes.

What I'd watch instead: clicks, revenue per person and spam complaints on the sends where you turned it off. Not opens. Apple Mail auto-opens pushed open rates past 85% on some segments in my data, so opens won't tell you much.

And keep the extra sends going to people who engage. Turning Smart Sending off for a restock to your engaged segment is a different decision than turning it off for a blast to everyone who's ever signed up.

What should you set before Black Friday?

Your offers, as early as you possibly can. Everything else hangs off them: the calendar, the anticipation sends, the early access, the subject lines. Lock the offers now, build the full calendar around them, and spend the first half of November driving hype toward the day they go live. Then do the Smart Sending pass: off on the flows that matter, off on the multi-send days, on for everything else.

Where these numbers come from

The unsubscribe and open rate numbers come from 4 consumable brands I work with: 2,897 campaigns and $17.7M in email revenue. It's a small sample, so treat it as directional. The subject line multiple comes from 3,176 Klaviyo campaigns across 9 brands. For how these brands compare on revenue per email, see my CPG email marketing benchmarks.

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WRITTEN BY Jack White

Founder of Bardown Digital, a Chicago-based Klaviyo email and retention agency for Shopify brands. He's worked with brands doing $500K to $100M a year, with $100M+ in email-attributed revenue across them.

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