Klaviyo Deliverability Guide 2026: Fix Inbox Placement & Stop Landing in Spam

Email deliverability is the foundation everything else is built on. You can have the best subject lines, the most perfectly timed flows, and the most compelling offers — but if Gmail is routing your emails to spam, none of it matters.

The good news: most Klaviyo deliverability problems are fixable in a single afternoon. The bad news: most brands don't know they have a deliverability problem until it's already significantly damaged their sender reputation.

This guide covers everything you need to diagnose and fix your Klaviyo deliverability — in the right order.

What Klaviyo Deliverability Actually Means

Deliverability refers to whether your emails reach the inbox — not just whether they're technically delivered. An email can be "delivered" (accepted by the receiving server) but still end up in spam, promotions, or the social tab.

Gmail, Outlook, and Apple Mail use complex algorithms to decide where your email goes. The main signals they look at:

• Sender reputation — how your domain and IP address have behaved historically
• Authentication — whether SPF, DKIM, and DMARC records are correctly configured
• Engagement signals — what percentage of your recipients open, click, and reply vs mark as spam
• List hygiene — how many invalid addresses, spam traps, and unengaged contacts you're sending to
• Content signals — certain words, link patterns, and HTML structures that trigger spam filters

Step 1: Fix Your Email Authentication

Authentication is the foundation. Without it, email providers have no way to verify that emails claiming to be from your domain actually are — and they'll treat them with suspicion accordingly.

Step 2: Set Up a Dedicated Sending Domain

By default, Klaviyo sends your emails from shared infrastructure — meaning your sender reputation is pooled with thousands of other brands. A dedicated sending domain (e.g. mail.yourbrand.com) builds reputation specific to your brand alone.

How to set it up:

1. Go to Klaviyo → Settings → Email → Sending Domains
2. Click Add Sending Domain
3. Enter a subdomain like mail.yourbrand.com or email.yourbrand.com
4. Klaviyo will give you DNS records to add at your domain registrar
5. Add the records and click Verify

Once set up, all emails send from your dedicated domain. Reputation builds specifically for your brand over 60–90 days. This is particularly important if you're sending more than 10,000 emails per month.

Step 3: Create Your Engaged Segment

This is the single highest-impact deliverability fix available — and it takes 20 minutes.

Every time you send to unengaged subscribers, you're training Gmail to treat your emails as unwanted. The algorithm sees low open rates as a signal to route future emails to spam — for everyone on your list, not just the unengaged contacts.

Create this segment in Klaviyo:

Brands that make this switch typically see open rates improve 30–60% within 30 days — from the same content, same subject lines, same everything. The only change is who they're sending to.

Step 4: Build a Win-Back Flow Before Suppressing

Before you suppress unengaged subscribers permanently, run them through a win-back sequence. Some will reactivate — and reactivated subscribers are often your most loyal customers.

A simple 4-email win-back:

• Day 90: "We miss you" — no offer, just a genuine reconnection email
• Day 105: What's new — product updates, brand news, something worth coming back for
• Day 120: Your best offer — maximum incentive for reactivation
• Day 130: "This is our last email" — creates urgency, often outperforms the offer email

Brands doing this reactivate 8–15% of lapsed subscribers. After Day 130, suppress anyone who still hasn't engaged — they're damaging your deliverability every time you send to them.

Step 5: Monitor Your Klaviyo Deliverability Hub

Klaviyo has a built-in Deliverability Hub that shows your key metrics. Go to Analytics → Deliverability and check these weekly:

• Bounce rate: Should be below 2%. Above 5% is a serious problem.
• Spam complaint rate: Should be below 0.08%. Above 0.1% will trigger Gmail filtering.
• Unsubscribe rate: Should be below 0.5% per send. Higher indicates irrelevant content or over-sending.
• Open rate: Below 15% on your engaged segment indicates deliverability issues.

Step 6: Clean Your List

List hygiene is an ongoing process, not a one-time task. Every month you should:

• Suppress hard bounces immediately — Klaviyo does this automatically, but verify in your suppression list
• Review soft bounces — contacts with 3+ soft bounces should be suppressed manually
• Remove role-based addresses — info@, admin@, hello@ addresses rarely belong to real people and often generate complaints
• Check for spam traps — old, abandoned email addresses can become spam traps that damage your reputation. Never buy email lists for this reason.

Step 7: Warm Up After a Deliverability Problem

If you've been sending to your full list and have poor deliverability, you can't fix it overnight. Gmail and Outlook need to see consistent good behaviour over time before they'll restore your inbox placement.

The warm-up process:

1. Immediately switch to your Engaged Segment only
2. Reduce sending frequency — if you were sending 3x per week, drop to 1x
3. Send your absolute best content — high engagement signals help rebuild reputation
4. Gradually increase volume over 4–6 weeks as metrics improve
5. Monitor Deliverability Hub weekly and only increase volume when complaint rate is below 0.05%

Klaviyo Deliverability Checklist