Most DTC brands treat email deliverability as someone else's problem. They set up Klaviyo, connect their domain, and start sending. And for the first few months, things seem fine. Open rates look acceptable. Revenue comes in. No one flags anything.
Then, quietly, performance starts to slip. Open rates drop. Campaign revenue softens. The win-back flow that used to pull 8% reactivation is barely hitting 3%. The culprit is almost never the copy. It is almost always deliverability.
This is the full breakdown of how email deliverability works in 2026, what is silently breaking it for most DTC brands, and the exact steps to fix it.
The Deliverability Problem Most Brands Don't Know They Have
Global inbox placement sits at 83.5% across all senders. For ecommerce specifically, it is lower. Retail and ecommerce brands sit at the bottom of inbox placement benchmarks across mainstream industries, pulled down by high promotional send volume, aggressive discount messaging, and list management that gets deprioritised the moment growth picks up pace.
That means roughly one in six of your marketing emails is not reaching the inbox. Some go to spam. Some disappear entirely, reported as missing in Validity's 2025 benchmark data, meaning they were neither delivered nor bounced, just gone.
An estimated 10.5% of permission-based marketing emails, sent to people who explicitly opted in, get filtered directly to spam. These are not cold outreach messages or unsolicited blasts. These are your flows, your campaigns, your welcome series, going to the spam folder of someone who asked to hear from you.
Email is your highest-margin revenue channel. If 10 to 16% of sends never reach the inbox, you are not running a broken email programme. You are running a functioning one with a structural leak.
What Actually Controls Whether Your Email Reaches the Inbox
Inbox providers like Gmail, Outlook, and Apple Mail run continuous reputation scores on your sending domain. Every send either strengthens or weakens that score. Five factors drive it.
Domain Authentication
Authentication is the baseline. Without it, inbox providers have no way to verify your emails are legitimate, and spam filters will treat them with suspicion regardless of engagement rates or list quality.
SPF (Sender Policy Framework) tells inbox providers which servers are authorised to send email on behalf of your domain. DKIM (DomainKeys Identified Mail) adds a cryptographic signature to every email, proving it has not been altered in transit. DMARC (Domain-based Message Authentication, Reporting, and Conformance) layers on top and tells inbox providers what to do when an email fails authentication.
In 2026, Gmail and Yahoo require DMARC for bulk senders. Despite this, 36% of email-sending domains still have no DMARC policy. If your brand sends promotional email and has not configured DMARC, you are sending unauthenticated mail to providers that are increasingly filtering it.
In Klaviyo, this means setting up a custom sending domain, not the default klaviyomail.com subdomain, and verifying SPF and DKIM records in your DNS. Klaviyo provides step-by-step DNS records for both. Once those are confirmed, add a DMARC record at the root domain level.
Sender Reputation
Inbox providers assign a reputation score to your sending domain and, in some cases, your IP address. That score is built over time based on how recipients interact with your emails.
High engagement, opens, clicks, replies, saves to primary inbox, strengthens your reputation. Spam complaints, deletions without opening, and low engagement rates weaken it. Once reputation is damaged, it takes weeks or months of disciplined sending to recover.
The trap most brands fall into is sending large campaigns to their entire list, including subscribers who have been inactive for six, twelve, sometimes eighteen months. Every send to an unengaged subscriber is a small vote against your reputation. Scale that across tens of thousands of contacts and you have a structural problem.
List Hygiene
A clean list is not a smaller list. It is a list of people likely to engage. Every hard bounce signals to inbox providers that your data is low quality. Hard bounce rates above 5% trigger reputation penalties that cascade across future sends.
More damaging than bounces are unengaged subscribers who do not bounce but also never open. They stay on your list indefinitely, silently pulling down your engagement rate. In Klaviyo terms, this is your 90-day unengaged segment, and for most DTC brands, it represents 20 to 30% of the total list.
The fix is not complicated. Suppress anyone who has not opened or clicked in 120 days, after running a re-engagement flow to give them one final opportunity. Set Klaviyo to automatically suppress hard bounces and spam complaints. Review quarterly.
Engagement Rate at Scale
Inbox providers do not just look at whether individual recipients open your emails. They look at your engagement rate across the full volume you send. If you send to 80,000 contacts but only 12,000 engage consistently, your domain reputation is calculated against the full 80,000, not the 12,000.
This is why segmentation is a deliverability strategy, not just a revenue strategy. Sending to your engaged segment first protects your average engagement rate. High-frequency sends should go only to your most engaged subscribers.
In Klaviyo, the benchmark for a healthy engaged segment is a 35% or higher open rate. If your campaigns are landing below 25% on your most active subscribers, the issue is not content. It is reputation.
Spam Complaint Rate
Gmail requires senders to maintain a spam complaint rate below 0.1% and will start to throttle delivery at 0.08%. If your rate exceeds 0.3%, Gmail treats your future mail accordingly.
Complaint rates spike when brands send to purchased lists, when unsubscribe links are hard to find, when send frequency is too high for an unengaged audience, or when the email content does not match what the subscriber signed up for. In Klaviyo, you can monitor complaint rates per campaign. Make this a standard part of your post-send review.
The Klaviyo Deliverability Audit: Six Things to Check Now
If you are not sure where your deliverability currently stands, run through this audit. Each step takes under fifteen minutes and will give you a clear picture of what is working and what is leaking.
Verify your custom sending domain
In Klaviyo, go to Account Settings then Sending Domains. If you are sending from the default Klaviyo subdomain rather than a custom domain like mail.yourbrand.com, fix this first. Custom sending domains dramatically improve deliverability because your sender reputation accumulates on your own domain rather than Klaviyo's shared infrastructure.
Check SPF, DKIM, and DMARC
Use MXToolbox to check your domain's DNS records. SPF adoption is at 93% in 2026, DKIM at 90%, but DMARC is only at 64%. If your DMARC is missing or set to p=none with no monitoring address, you have no visibility into authentication failures. Set up DMARC with at least a reporting address so you can see what is failing.
Pull your Klaviyo account health score
Klaviyo gives each account a deliverability health score. It should be 95 or above. If it is below 90, there is an active problem. Review the specific signals Klaviyo flags: bounce rate, complaint rate, and engagement rate per send. Address the lowest-scoring area first.
Build your engaged segment
Create a segment in Klaviyo: opened or clicked any email in the last 90 days. This is your deliverable audience. Compare its size to your total active list. If your engaged segment is less than 50% of your active list, your deliverability is at risk on every campaign you send to the full list.
Run a sunset flow for unengaged subscribers
Build a three-email re-engagement sequence for anyone who has not opened in 90 days. Email one: a direct ask to confirm they want to stay on the list. Email two, sent five days later: a reason to come back, your best offer, a new product, a strong piece of content. Email three, sent five days after that: a final goodbye. If they do not engage with any of the three, suppress them. This is about protecting the deliverability of every email you send to the people who do engage.
Set up Klaviyo deliverability monitoring
In Klaviyo's deliverability dashboard, track six metrics weekly: deliverability rate (target above 98%), bounce rate (below 2%), spam complaint rate (below 0.1%), open rate on your engaged segment (target above 35%), unsubscribe rate per send (normal is 0.1 to 0.2%), and your account health score (95 or above). Put these in a shared dashboard so your entire team, or your agency, can see them without asking.
What Deliverability Recovery Actually Looks Like
A food and beverage brand I worked with had a Klaviyo list of 52,000 contacts and was generating around 14% of revenue from email. Open rates had been declining for eight months. Campaigns were returning roughly half of what they had six months earlier. Their agency attributed it to creative fatigue and kept testing new subject lines.
The actual problem was deliverability. They had no custom sending domain, no DMARC record, and had never run a list suppression. Their engaged segment was 18,000 contacts, 35% of their list, but they were sending every campaign to all 52,000. Their average engagement rate across the full send was 13%, well below the 25% threshold that triggers Gmail's deprioritisation filters.
We set up the custom sending domain, configured DMARC, ran the sunset flow, and suppressed 21,000 contacts who had not engaged in 120 days. Campaigns then went to the 31,000 active subscribers. Open rates jumped from 19% to 38% within 30 days, not because the content improved, but because the audience was the engaged one.
Email revenue as a percentage of total revenue went from 14% to 31% over 90 days. Same brand, same Klaviyo account, same team. Deliverability was the lever. Everything else was already there.
The Sending Warmup Problem for New Domains
If you are setting up a custom sending domain for the first time, or switching to a new domain, you cannot immediately send to your full list. Inbox providers have no reputation history for the new domain and will treat high-volume sends as suspicious.
Warmup means starting with small send volumes to your most engaged subscribers and gradually increasing over four to six weeks. Week one: send to your top 500 engaged contacts only. Week two: expand to 2,000. Week three: 8,000. By week six, you have built enough positive sending history to handle full-list campaigns without triggering filters.
Klaviyo has a built-in warmup mode for new sending domains. Use it. Brands that skip warmup and send to their full list from a new domain often crater their reputation in the first 30 days and spend months trying to recover it.
Deliverability and Revenue: The Direct Line
For a DTC brand generating 500,000 GBP per year with email driving 25% of revenue, that is 125,000 GBP annually from email. If deliverability issues mean 15% of sends never reach the inbox, you are losing 18,750 GBP per year from the channel you have already built and already paid for.
That is a conservative number. Most brands with deliverability problems are losing more, because degraded reputation affects the opens and clicks of the emails that do land, not just the ones that get filtered. Every send to an unengaged list hurts the next send, and the one after that.
Deliverability is not a technical nice-to-have. It is the foundation everything else in Klaviyo sits on. If the foundation is cracked, your flows, your campaigns, and your automations are all underperforming, and you will never find the answer in subject line A/B tests.
Growth Audit
Find Out What Your Email Programme Is Actually Worth
I will review your Klaviyo setup, check your deliverability health, and tell you exactly where the revenue is leaking. No pitch deck. No fluff. Just the numbers and what to do about them.
Book Your AuditFrequently asked questions
Why are my Klaviyo emails going to spam?
The most common causes are missing or misconfigured domain authentication (SPF, DKIM, DMARC), sending to a large proportion of unengaged subscribers, high bounce rates, or a spam complaint rate above 0.1%. In Klaviyo, check your account health score and review your bounce and complaint rates. Start by auditing your domain authentication settings, then segment your list to send only to engaged contacts.
What is a good email deliverability rate for ecommerce brands in 2026?
A good inbox placement rate for ecommerce brands is 90% or above. The global average is 83.5%, but ecommerce sits at the lower end of mainstream categories due to high promotional send volume. If your Klaviyo open rates on engaged segments fall below 25%, or your spam complaint rate exceeds 0.1%, you likely have a deliverability problem worth investigating.
How do I set up DMARC for my Klaviyo account?
First, verify that SPF and DKIM are configured for your sending domain in Klaviyo. Then add a DMARC TXT record to your DNS: v=DMARC1; p=none; rua=mailto:[email protected]. Start with p=none to monitor, then move to p=quarantine and eventually p=reject once you confirm no legitimate emails are failing. DMARC is required by Gmail and Yahoo for bulk senders sending over 5,000 emails per day.
How often should I clean my Klaviyo email list?
Review your list every 90 days. Suppress contacts who have not opened or clicked in 120 days after running a re-engagement sequence. Hard bounces should be suppressed immediately. Remove contacts with spam complaints at once. For most DTC brands, 20 to 30% of their Klaviyo list is unengaged and actively damaging deliverability by pulling down engagement rates.
Does sending frequency affect email deliverability?
Yes. Sending too frequently to a cold or unengaged list is one of the fastest ways to trigger spam filters. Inbox providers measure engagement rate across your sends, not just individual opens. If you send to 100,000 contacts but only 15,000 engage, your reputation scores against the full 100,000. Segment your list and send high-frequency campaigns only to your engaged segment. Reduce cadence for everyone else.
What Klaviyo metrics should I monitor for deliverability health?
Monitor these six metrics in Klaviyo: deliverability rate (target above 98%), bounce rate (keep below 2%, investigate above 5%), spam complaint rate (keep below 0.1%), open rate on your engaged segment (target above 35%), unsubscribe rate per send (normal is 0.1-0.2%, investigate above 0.5%), and Klaviyo account health score (should be 95 or above).
About the author
Caner Veli built Liquiproof from zero to 3,000+ global retailers in under 6 years. He now helps DTC and CPG brands fix broken growth engines and scale 2x-15x in 90 days.