Deliverability is the part of email marketing nobody wants to think about until it breaks. Then it is the only thing that matters, because a campaign that lands in spam makes nothing, however good the offer is. The uncomfortable truth is that most deliverability problems are self-inflicted: sending to people who stopped opening months ago, skipping the domain setup, or blasting a brand-new account at full volume on day one.
This guide covers the whole picture for Klaviyo: how to set the account up so you start clean, how to send so you stay clean, how to read the reports that tell you something is going wrong, and how to recover when it already has. Each section links to the detailed walkthrough.
How inbox providers decide where your email goes
Gmail, Yahoo, Outlook and Apple decide whether to put your email in the inbox, the promotions tab or spam based on your reputation as a sender. That reputation is built from how people react to your email: opens, clicks, replies and moving it out of spam count for you; deletes without opening, spam complaints and bounces count against you. It is tied to both your sending domain and the IP addresses Klaviyo sends from, which is why a shared sending domain can be a problem and a dedicated one is usually worth it.
The practical consequence is simple. Every email you send to someone who ignores it costs you a little reputation, and every email you send to someone who engages earns some back. Deliverability is mostly about controlling who you send to.
Setting up your sending domain and authentication
Before you worry about engagement, get the technical foundation right. There are three pieces.
- A branded sending domain, so your emails come from your own domain rather than a shared Klaviyo one: How to Set Up a Branded Sending Domain in Klaviyo.
- A dedicated sending domain once you are sending at volume, so your reputation is yours alone: How to Set Up a Dedicated Sending Domain in Klaviyo.
- Authentication (SPF, DKIM and DMARC), which Google and Yahoo now require from bulk senders: How to Set Up Authentication for Google and Yahoo in Klaviyo.
If the account is brand new, the full setup is in Getting Started with Klaviyo: The Complete Setup Guide. If you are on Omnisend, the equivalent is How to Set Up Your Omnisend Account the Right Way.
Warming up a new account or domain
A new sending domain has no reputation, and inbox providers treat no reputation as suspicious. If you move a large list across and send to all of it on day one, you will land in spam and it will take weeks to climb out. The fix is a warm-up: start by sending only to your most engaged subscribers, then widen the audience a step at a time over a few weeks as the reputation builds. The schedule I use is in How to Warm Up a New Klaviyo Account and Hit Primary.
Sending to engaged segments
This is the single biggest lever. Campaigns should go to an engaged segment, not the whole list. An engaged segment is typically everyone who has opened or clicked in the last 30, 60 or 90 days, plus anyone who has bought or signed up recently. The exact window depends on how often you send and how big the list is.
The segments I use are in The Only Klaviyo Segments You Need to Maximise Sales, and the deliverability-specific version in How to Fix Email Deliverability with Engaged Segments. If deliverability has already dropped and you need a segmentation plan to rebuild it, read Fixing Broken Campaign Deliverability with Klaviyo Segments. Omnisend users: How to build high-converting segments in Omnisend.
Sending to engaged people only does not mean the rest of the list is wasted. Cold subscribers can be re-engaged on their own terms, with a separate campaign that asks them to opt back in: How to Re-Engage Cold Klaviyo Subscribers with Campaigns.
Cleaning your list
Engaged segments stop you emailing cold profiles. List cleaning removes them, which also cuts your Klaviyo bill, because you pay for every active profile whether or not you email them. The process is in How to Clean a List in Klaviyo to Protect Deliverability, with the cost angle in How to Lower Your Klaviyo Bill by Cleaning Unengaged Profiles.
The automated version of cleaning is a sunset flow, which gives inactive subscribers a last chance and then suppresses them: How to Build a Klaviyo Sunset Flow That Protects Deliverability.
Bounces and list bombing
Two problems that look like engagement issues but are actually list quality issues. High bounce rates usually mean bad addresses are getting in through your forms: How to reduce high email bounce rates in your Klaviyo account. List bombing is when bots flood your sign-up form with fake or stolen addresses, which then bounce or complain: How to Identify and Fix List Bombing in Klaviyo. Part of the answer is your opt-in setting, covered in Single Opt-In vs Double Opt-In for Ecommerce Brands.
Getting out of the promotions tab
Landing in Gmail's promotions tab is not the same as landing in spam, and for most ecommerce brands it is where your campaigns belong. But flows and plain-text emails that should feel personal do better in the primary inbox. What moves an email between the two, and what you can do about it, is in Why Your Emails Land in Promotions and How to Fix It. Plain text is the most reliable tool here: How to Use Plain Text Emails in Klaviyo for Higher Opens.
Gmail is also changing how it summarises and sorts email with AI, which affects what gets seen. See How Gmail's Gemini AI Update Changes Email Marketing.
Reading the deliverability reports
Klaviyo tells you when something is going wrong, but only if you look. The numbers to watch are open rate by inbox provider, spam complaint rate, bounce rate and unsubscribe rate, and the thing to look for is a change: a drop in Gmail opens while Yahoo stays flat points at a Gmail reputation problem, not a subject line problem.
Where to find these and what they mean: How to Review Your Deliverability Inside Klaviyo, How to Use Klaviyo Deliverability Reporting for Campaigns and Important Klaviyo Metrics to Review for Campaign Deliverability. For flows, which are easy to forget because they run in the background, see How to Build a Klaviyo Flow Deliverability Report.
If opens have fallen and you are not sure whether it is deliverability or content, start with Why Your Emails Aren't Getting Opened (And How to Fix It).
Recovering from a deliverability problem
When you are already in spam, the recovery is the warm-up process in reverse: stop sending to everyone, send only to your most engaged people, keep the volume low and consistent, and widen the audience slowly as the numbers improve. It usually takes a few weeks. The full recovery plan is in How to Fix Klaviyo Deliverability and Stop Landing in Spam, and a real example of a fast turnaround in How We Rescued Ecommerce Email Deliverability in 7 Days.
Sending cadence
How often you send affects deliverability in both directions. Sending too rarely means inbox providers never build a stable picture of you, and subscribers forget who you are. Sending too often to the whole list burns engagement. The answer for most brands is more often than they think, but to a tighter audience. See How to Set the Right Sending Cadence for Email Campaigns and Why Sending More Email Campaigns Increases Your Revenue.
The checklist
- Branded or dedicated sending domain, with SPF, DKIM and DMARC passing.
- New domains and accounts warmed up over several weeks, not switched on at full volume.
- Campaigns sent to an engaged segment, never the whole list.
- A sunset flow running, and a list clean at least twice a year.
- Double opt-in or bot protection on forms if bounces or list bombing show up.
- Deliverability reports checked monthly, with open rate by provider as the early warning.
If you would rather have someone check all of this for you, our Klaviyo account audit covers deliverability end to end, and our Klaviyo account setup gets a new account started the right way.
