The Inbox Booster helps more of your emails land in the primary inbox instead of the Promotions tab or spam. More inbox placement means more opens, more clicks, and more revenue from the sends you're already making, without changing your content, list, or send schedule.

It covers all of your Klaviyo marketing emails, flows and campaigns alike. Once it's on, Zaymo adds the booster for you, so there's nothing to design or maintain.

How it works

Mailbox providers like Gmail, Apple Mail, and Outlook look at many signals to decide whether a message lands in the inbox, the Promotions tab, or spam.

The Inbox Booster adds a small, invisible block of code to your emails that strengthens those signals. Subscribers never see it, and it doesn't change how your email looks or reads.

Getting started

1. Go to the Inbox booster page in Zaymo and click Get Inbox booster. Pricing is based on the number of profiles in your Klaviyo account.

2. Connect Klaviyo if you haven't already.

3. Zaymo adds the booster to your Klaviyo emails automatically and keeps checking for new ones.

The status at the top of the Inbox booster page shows where things stand:

• Syncing: the booster is being added, or your first boosted emails haven't been out long enough to report results.

• Auto adding: the booster is live and results are coming in.

• Not connected: connect Klaviyo to get started.

• Not enabled: click Enable for all emails to turn it on.

• Paused: the booster is off. Contact your Zaymo team to resume it.

Which emails are boosted

• Flows: emails in your Klaviyo flows.

• Campaigns: draft and scheduled campaigns. A campaign scheduled less than 30 minutes before it sends may go out without the booster. A scheduled campaign that uses Smart Send Time, throttled sending, each recipient's local time zone, or an A/B test isn't changed once it's scheduled, so it goes out without the booster.

• Templates and universal content: your saved Klaviyo templates and the universal content blocks your emails use.

A few emails aren't boosted:

• Transactional emails.

• Emails that have already been sent. The booster only applies going forward.

• Emails you've removed the booster from. If you take it out of an email, Zaymo won't add it back.

How lift is measured

Because "deliverability went up" is easy to claim and hard to prove, Zaymo measures results with a built-in holdout.

Each send is automatically split between a boosted group and a small control group, about 6% of recipients by default, who don't receive the booster. Comparing the two groups shows what the booster added, separate from things like seasonality or a strong subject line.

Reading your results

The Inbox booster page shows:

• Open rate lift and Click rate lift: how the boosted group compares with the control group.

• Est. revenue impact and Revenue per recipient lift: what that difference means in revenue.

• Lift by email: results for each boosted email.

A lift of +18% means boosted recipients opened about 18% more often than the control group. A "—" means there isn't enough data yet, because Zaymo waits for a meaningful sample so you don't react to noise.

Results appear once your first boosted send has been out for 48 hours, and it's normal for data to take a few days to settle. Small sends take longer, since both groups need to be large enough to compare.

Pausing or canceling

Contact your Zaymo team to pause, resume, or cancel the Inbox Booster.

Requirements and troubleshooting

• The Inbox Booster works with Klaviyo only. Klaviyo must be connected with the right permissions, so reconnect if prompted.

• If you don't see lift yet, check that the email has been out for at least 48 hours and has reached enough recipients.

• Open rates can be noisy for unrelated reasons. The control group comparison separates the booster's effect from that noise.

FAQ

Will subscribers see anything different?

No, it's invisible.

Does it change who I send to or when?

No, it only affects inbox placement.

Why does a small group not get the booster?

That's the control group, held out to measure lift.

Do I need to add anything to my emails?

No. Zaymo adds the booster for you.

How fast are results?

Results appear once your first boosted send has been out for 48 hours.