Email Deliverability Best Practices: 8 Rules for DTC Brands

One in eight marketing emails never reached the inbox in 2025.

Validity's 2026 deliverability benchmark put global inbox placement at 87.2%, with 6.6% landing in spam and another 6.1% going missing entirely. For a DTC brand earning a third of its revenue from Klaviyo, that gap is real money.

It also gets worse at the exact moment it matters most. Black Friday is the week brands double their send volume, pull old segments back into rotation and test Gmail's patience.

Gmail started ramping up enforcement on non-compliant bulk mail this November, so the margin for sloppy sending is thinner than last year.

These are the email deliverability best practices we run on every DTC account we manage: 8 rules covering authentication, complaint rates, segmentation, unsubscribes, sunset flows, BFCM warm-up, provider-level reporting and list growth. Then we'll walk through how to diagnose a Klaviyo account that has already slipped into spam.

What is email deliverability, and what counts as good?

Delivery and deliverability get mixed up constantly. Delivery means the receiving server accepted your email. Deliverability means it landed in the inbox instead of the spam folder or nowhere at all. Klaviyo can report a 99% delivery rate on a send that mostly went to spam.

Inbox placement is the number to care about, and it varies a lot by mailbox provider. In the Validity 2026 report, Gmail placed 89.8% of marketing mail in the inbox and Yahoo 87.3%. Apple sat at 82.0% and Microsoft trailed at 77.4%.

Most US DTC lists skew heavily toward Gmail, which is why many brands never notice a problem until a big send goes sideways. A good target is inbox placement above 90% at Gmail with bounce rates under 1%.

"Global inbox placement was 87.2% in 2025, with 6.6% of marketing email in spam and 6.1% missing." — Validity, 2026 Email Deliverability Benchmark

Rule 1: Authenticate your domain with SPF, DKIM and DMARC

Authentication proves to Gmail and Outlook that you are who you say you are. Google's sender guidelines treat anyone sending close to 5,000 messages a day to personal Gmail accounts as a bulk sender, and that status is permanent once you hit it.

Bulk senders need SPF and DKIM, plus a DMARC record with the From domain aligned to one of them. In Klaviyo that means setting up a branded sending domain, which its deliverability reference recommends for any account with 5,000 or more active profiles.

Start DMARC at p=none so you can read the reports without blocking anything, then move to quarantine once your sources are clean. Shopify's notification emails, your help desk, your review app and any loyalty platform need to pass too, or you'll see failures stacking up in the DMARC reports.

Rule 2: Keep spam complaints under 0.1% with 0.3% as the wall

Gmail asks senders to keep their spam rate below 0.1% and to prevent it from ever reaching 0.3%. Above 0.3%, you lose eligibility for mitigation, and from November 2025 Gmail has been ramping up rejections of non-compliant traffic.

In our experience running Klaviyo for DTC brands, the accounts that hit spam are rarely the ones with weak copy. They're the ones mailing the full list twice a week. Across the 20 DTC brands in our email marketing benchmark, more than 82 million campaign emails, the median spam complaint rate was 0.02%. That's a fifth of Gmail's target, and it came from engagement-based segmentation, with no special tooling involved.

Track the rate on every campaign. A monthly average hides the single 0.4% send to a stale segment that can undo weeks of clean sending.

"Across 20 DTC brands and more than 82 million campaign emails, the median spam complaint rate was 0.02%, a fifth of Gmail's 0.1% target." — Top Growth Marketing, DTC email marketing benchmark, 2026

Rule 3: Send campaigns to engaged segments first

Mailbox providers watch how your recipients behave. Opens, clicks, replies and moves out of spam all count, and so do deletes without opening. Every unengaged recipient on a campaign is a small vote against your reputation.

Build engagement tiers in Klaviyo and send your default campaigns to the tightest one. A practical setup uses a 30-day engaged segment for most sends. Bigger promos can go to the 60-day group, and product launches earn the 90-day group. Expand only when the narrower send shows clean complaint and bounce numbers.

Define engaged by clicks, site visits, Active on Site events and orders. Apple Mail Privacy Protection inflates opens, which is why our benchmark reports a 50.5% median open rate. An open-only definition will keep plenty of people who stopped reading months ago.

Our guide to Klaviyo segmentation strategies covers how to build these segments in detail.

Rule 4: Make unsubscribing a one-click job

An unsubscribe costs you a subscriber. A spam complaint costs you a subscriber and damages delivery to everyone else. Make the first easier than the second.

Gmail requires one-click unsubscribe headers for bulk marketing mail and recommends honoring requests within 48 hours. Klaviyo adds the header automatically, but check that your footer link is visible on mobile and that nobody has styled it in light grey at 9px.

Add a preference page so people can drop to a monthly email instead of leaving. For a list that buys seasonally, a frequency-down option keeps profiles you'd otherwise lose, and those profiles come back for Black Friday.

Rule 5: Run a sunset flow every month

A sunset flow is the last attempt to win back a profile before you stop mailing it. Trigger it when someone has gone 180 days without a click, site visit or order, send two or three emails asking whether they still want to hear from you, then suppress anyone who stays silent.

Sunset flows earn very little directly, and our email flow benchmark shows them near the bottom on revenue per recipient by design. Their job is protecting the revenue every other flow earns.

Watch bounces alongside it. Klaviyo's guidance is a bounce rate under 1.0% and an unsubscribe rate under 0.3%. If bounces climb after a list import or a giveaway, clean the list before your next big send. Our winback campaign guide covers the step before a sunset, when lapsed customers are still worth chasing.

Rule 6: Ramp volume over four weeks before Black Friday

Mailbox providers dislike sudden volume spikes from a sender. The classic BFCM mistake is a brand sending to 40% of its list all of November, then mailing 100% of it on Black Friday morning, including profiles that last opened in 2024.

Start the ramp four weeks out. Week one goes to your 30-day engaged tier. Week two adds the 60-day tier, week three the 90-day tier, and the week before Black Friday adds 120-day profiles. On the day itself, cap the send at 180-day engaged and keep never-engaged profiles out entirely. Reading this with less than four weeks to go? Add one tier every five days instead.

Space your big sends a few hours apart rather than queuing four campaigns for 6am. Our BFCM marketing playbook covers the offer and creative side of the same calendar.

Rule 7: Report placement by mailbox provider

A blended open or delivery rate hides provider-level problems. Microsoft is the usual culprit. In the Validity data, Microsoft sent 15.1% of marketing mail to spam, more than double Gmail's 6.4%.

In Klaviyo, build a segment by email domain (outlook.com, hotmail.com, live.com) and compare its click rate to your Gmail segment over the last 90 days. If the Microsoft group clicks at less than half the Gmail rate, you likely have a placement issue with Microsoft, because the same content performs fine at Gmail.

Register for Google Postmaster Tools so you can see your Gmail spam rate directly. Klaviyo's own deliverability score needs at least 1,000 emails sent in the past 30 days, so smaller senders should lean on Postmaster data instead.

"Microsoft sent 15.1% of marketing email to spam in 2025, more than double Gmail's 6.4%." — Validity, 2026 Email Deliverability Benchmark

Rule 8: Keep list growth clean at the source

Most deliverability problems start at signup. Purchased lists and co-registration deals are the obvious culprits. Loosely gated giveaways do the same damage more slowly, pulling in addresses that never wanted your email plus the occasional spam trap that flags you as a sender who doesn't clean lists.

Turn on double opt-in for any giveaway or sweepstakes form, and add bot protection to your popups. Ten thousand fake signups in a weekend can wreck a domain that took a year to build.

Send new subscribers a welcome series right away, while interest is high. The first email after signup is the best engagement signal you'll ever get from that profile. Our welcome email series guide lays out the sequence we build first.

Why are my Klaviyo emails going to spam?

Diagnose before you rewrite anything. Copy is the last thing to blame. Work through four checks in order.

First, open Klaviyo's deliverability hub and check the score and the trend on complaints and bounces. Second, pull your Gmail spam rate from Postmaster Tools for the last 30 days. Third, compare click rates by mailbox provider as described in Rule 7. Fourth, look at the segment sizes on your last 10 campaigns. If they grew while engagement fell, you've found the cause.

The fix is almost always the same. Narrow campaign segments to 30-day engaged for two weeks while the sunset flow clears out dead profiles, and the reputation rebuilds on its own. Most accounts we've repaired recover within a few weeks of cleaner sending.

It pays to move fast. If an email program would earn $60,000 a month at the 87.2% global placement average, dropping to Microsoft-level placement of 77.4% costs about $6,700 a month, assuming revenue scales with inbox placement. Use our email open rate calculator to set your own baseline.

Your deliverability checklist before Black Friday

Three things decide most of your inbox placement this season. Authentication has to pass for every tool that sends as your domain. Complaints need to stay under Gmail's 0.1% line on every single campaign. And volume should climb tier by tier through November instead of spiking on the day.

If you want a second pair of eyes on your Klaviyo account before the big sends, book a growth strategy call. Our Klaviyo email and SMS team will check your segments, sunset flow and provider-level placement, and our ecommerce email marketing playbook covers the rest of the program.

Last updated: November 8, 2026

Written by

Jack Paxton

Jack Paxton is the founder of Top Growth Marketing, a DTC and eCommerce growth agency. He works hands-on with Shopify and DTC brands on paid social, Google Ads, and Klaviyo email and SMS.

Founder of Top Growth Marketing · $336M+ managed ad spend · 218+ DTC brands scaled

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