Your last campaign didn’t underperform. It underdelivered. There’s a difference, and most founders never see it, because Klaviyo will happily report that an email was “sent” whether it landed in the primary inbox or a spam folder nobody has opened since 2019.
Here’s the uncomfortable math: if your list has 50,000 profiles and 20% of your sends are quietly routed to spam, you are invisible to 10,000 people who asked to hear from you. No design fix, no subject line test, no discount will recover them, because they never saw the email. Deliverability isn’t one factor among many. It’s the gate every other decision has to pass through first.
The 2024 rule change most brands still haven’t caught up with
In February 2024, Google and Yahoo stopped asking nicely. Bulk senders to Gmail addresses now face hard requirements: authenticate your email with SPF and DKIM, publish a DMARC policy, offer one-click unsubscribe, and keep your spam complaint rate below 0.3%. Google’s own guidance is blunter: stay under 0.1%, because sustained complaints near the threshold get your mail filtered regardless of how good the content is. Microsoft began enforcing similar requirements for high-volume senders to Outlook, Hotmail, and Live addresses in May 2025, and Gmail moved from warnings to hard enforcement in November 2025, rejecting non-compliant mail rather than just filtering it. Unsubscribe requests now have to be honored within 48 hours.
Translation for DTC founders: the era where you could skip the technical setup and coast on a decent offer is over. The inbox providers now check your paperwork at the door.
The five leaks we find in almost every account
1. You’re sending from a domain you don’t control. Many accounts still send through a shared sending domain, the platform default. Your reputation gets pooled with strangers, and when one of them blasts a scraped list, everyone in the pool pays. The fix is a dedicated sending domain: your brand, your reputation, your record. It’s also the first thing we check in any audit, because nothing else matters until it’s true.
2. Your authentication is incomplete, and you’ve never checked. SPF, DKIM, and DMARC are three DNS records that prove you are who you claim to be. Miss one, most commonly DKIM alignment or a missing DMARC policy, and inbox providers treat you as unverified. We routinely open accounts where one record passes, one fails, and nobody has looked since setup day. It takes a specialist about ten minutes to check. Most brands go years without doing it.
3. You’re mailing the dead. Every list accumulates ghosts: bounced addresses, spam-trap risks, subscribers who haven’t opened in a year. Sending to them tells Gmail your mail isn’t wanted, drags your engagement rates down, and inflates your Klaviyo bill, because you pay for profiles whether they read you or not. The fix is unglamorous: engagement-tiered segments, a sunset flow that gives the unengaged one last chance, and the discipline to actually suppress what’s dead.
4. Your “opens” are lying to you. Since Apple’s Mail Privacy Protection, a large share of open events fire automatically whether the human looked or not. Brands celebrating 50% open rates are often reading machine noise. Judge engagement by clicks and revenue per recipient, and configure your account so inflated opens aren’t steering your segments.
5. You blast, then vanish, then blast again. Two campaigns in January, nothing until a panicked April send, then seven in one week before a launch. Inbox providers read erratic volume as spammer behavior, because it is spammer behavior, spammers spike; brands with relationships send consistently. A steady calendar isn’t just strategy. It’s reputation maintenance.
A beautiful email in the spam folder is worth exactly nothing. Infrastructure comes before decoration, every time.
What “fixed” actually looks like
One brand we rebuilt came to us with a Klaviyo deliverability score of 74, the “Fair” band, where mail is already leaking to spam. Setup was the usual story: shared sending infrastructure, incomplete authentication, unengaged profiles mixed into every send.
The rebuild was boring and sequential: dedicated sending domain, all three authentication records configured and verified, list hygiene pass, engagement-tiered segments, and a consistent sending calendar. Five months later the score sat at 91, “Excellent.” Open rate up from 45% to 57%. Bounce rate down from 0.70% to 0.16%. Spam complaints at 0.005%, a quarter of the previous level, and comfortably inside Google’s strictest guidance.
Nothing about the products changed. Nothing about the offer changed. The inbox simply started trusting the sender, and every email after that worked harder.
The 10-minute self-check
Before you hire anyone, check three things yourself:
- Klaviyo’s deliverability score (inside your account): below 85 means money is leaking.
- Your sending domain: open a recent campaign’s technical details. If you’re not sending from a branded, dedicated domain, that’s leak number one.
- Your spam complaint trend: anywhere near 0.3% is an emergency; above 0.1% is a warning. The complaint-rate playbook covers the recovery path.
If any of the three fails, the problem is almost never the emails. It’s the infrastructure underneath them, and infrastructure problems have checklists, not mysteries.
Related reading: BIMI: Getting Your Logo in the Inbox (And Whether It’s Worth It), Gmail’s Promotions Tab: Escape Attempts, Ranked by Honesty, Ecommerce Subject Lines: Formulas, Not Magic Words, The Weekly Email Dashboard: 7 Numbers Founders Should Actually Read.
Would you rather hand the whole program over? Our end-to-end Klaviyo account management runs strategy, campaigns, flows, and reporting for you.
Quick answers
Why are my emails suddenly going to spam? Usually a reputation change: a complaint spike, a send to old or unengaged profiles, or an authentication record that broke after a DNS or platform change. Check Google Postmaster Tools and your DMARC reports first.
Do I need DMARC to send to Gmail? Yes, if you send in bulk. Gmail and Yahoo require SPF, DKIM, and a DMARC record for bulk senders, and Gmail now rejects non-compliant bulk mail instead of just filtering it. The setup is explained in DMARC, DKIM, and SPF in plain English.
What spam complaint rate is safe? Stay below 0.1% in Postmaster Tools and never reach 0.3%. Above 0.3%, Gmail stops helping with delivery problems until you spend seven straight days below it. More in the 0.3% complaint cliff.
Want to know if your mail is actually arriving? The free Health Score checks authentication, sending domain, complaint signals, and list hygiene among 75+ checkpoints across 8 systems, and prices every leak in dollars. Delivered within 72 hours of access. Get your Health Score →
