Email Deliverability Guide
Your emails aren't underperforming. They're going to spam.
Most eCommerce brands think they have an email content problem. They don't. They have a deliverability problem — and they don't know it because Klaviyo still shows the emails as "sent." But sent doesn't mean delivered. And delivered doesn't mean inbox.
Here's what to fix right now. Step 1: Go to mail-tester.com, send yourself a test email, and check your spam score. Anything below 7/10 means you have technical issues — missing authentication records, blacklisted IPs, or content triggers. Step 2: Set up a dedicated sending domain in Klaviyo. Don't send from your root domain (yourbrand.com) — use send.yourbrand.com with properly configured SPF, DKIM, and DMARC records. This protects your root domain reputation if something goes wrong. Step 3: Check if you're on any blacklists. Go to mxtoolbox.com/blacklists.aspx and enter your sending domain. If you're listed anywhere, that's your problem — and the delisting process varies by blacklist but starts with fixing whatever got you listed.
Those three diagnostic steps take under 30 minutes. The full repair playbook is below.
21%
Emails That Never Reach Inbox
7/10+
Healthy Spam Score
0.3%
Max Spam Complaint Rate
99.5%
Target Delivery Rate
How to fix this — step by step
Run a spam score test right now
Go to mail-tester.com. It gives you a unique email address. Send a test campaign from Klaviyo to that address. Within seconds, you get a score out of 10 with a detailed breakdown of what's wrong. Below 7 means technical problems. Below 5 means you're almost certainly hitting spam for a significant portion of your list. This takes 2 minutes and gives you a clear starting point. Do it before anything else.
Set up a dedicated sending domain with full authentication
In Klaviyo, go to Settings → Email → Sending Domains. Add a subdomain like send.yourbrand.com or mail.yourbrand.com. Klaviyo generates SPF, DKIM, and DMARC records — add them to your DNS provider (GoDaddy, Cloudflare, Namecheap, wherever). SPF tells inbox providers which servers can send on your behalf. DKIM cryptographically signs your emails. DMARC tells providers what to do when checks fail. All three are mandatory since Gmail and Yahoo's February 2024 updates.
Check and resolve any blacklist issues
Visit mxtoolbox.com/blacklists.aspx and enter your sending domain and IP. If you show up on any blacklists (Spamhaus, Barracuda, SORBS), that's likely the primary cause of your deliverability problems. Each blacklist has a specific delisting process — usually you submit a request and demonstrate you've fixed the underlying issue (spam complaints, purchased lists, etc). Klaviyo's shared IP pools can sometimes get you caught up in another sender's bad behavior, which is another reason to move to a dedicated sending domain.
Suppress complainers and bounces aggressively
In Klaviyo, set hard bounces to suppress after 1 occurrence and soft bounces after 3-5. Never re-add a hard bounce — it's a dead address and hitting it repeatedly damages your reputation. Set up a suppression rule for anyone who marks you as spam (Klaviyo does this automatically, but verify it's working). Keep your spam complaint rate below 0.3% — Gmail will throttle you above that threshold. If you're above 0.1%, you need to clean more aggressively.
Segment sends by engagement level
Stop sending every campaign to your entire list. Create engagement tiers in Klaviyo: Active (opened/clicked in 30 days), Engaged (opened/clicked in 31-90 days), At-Risk (91-180 days), Inactive (180+ days). Send campaigns only to Active and Engaged segments. At-Risk gets a re-engagement flow. Inactive gets suppressed. This alone can lift inbox placement by 15-25% because you're sending only to people who want to hear from you — which is the #1 signal inbox providers look for.
Warm your sending domain properly after cleanup
After setting up authentication and cleaning your list, don't blast a campaign to 50,000 people. You need to warm your domain. Week 1: send to your most engaged 500-1,000 subscribers. Week 2: expand to 2,000-5,000. Week 3: 10,000. Week 4: full engaged list. Each week, monitor your open rates and spam complaints. If opens drop below 25% or complaints spike above 0.1%, slow down. Warming properly takes 3-4 weeks. Rushing it puts you right back in spam.
Monitor ongoing deliverability with inbox placement testing
Deliverability isn't a one-time fix. It requires continuous monitoring. Tools like GlockApps or Inbox Monster let you see exactly which inbox providers are putting you in spam, promotions, or primary. Run placement tests monthly — or before any major campaign (BFCM, product launches). Track your sender reputation score over time. Watch for sudden drops in open rates which often signal a deliverability issue before you even know about it. This kind of ongoing monitoring is where having a dedicated team makes the difference.
Want us to handle this?
Steps 1 through 5 are diagnostic work you can do yourself. Run the tests, fix the authentication, clean the list, segment your sends. You'll see improvement within 2-4 weeks.
Steps 6 and 7 — domain warming, ongoing placement testing, and the continuous monitoring that keeps you out of spam — take time and specialized tools that most brands don't have in-house. As a Klaviyo Gold Partner, we handle deliverability remediation from start to finish. We'll audit your current setup, fix the technical issues, rebuild your sending reputation, and keep it healthy. The initial audit is free and we deliver it within 48 hours.
Questions our best clients asked first
Are your emails actually reaching the inbox?
We'll run a full deliverability diagnostic — spam score, authentication check, blacklist scan, and inbox placement test. You'll know exactly where you stand within 48 hours. Free.
Pick a Time15 minutes. No pitch deck. Just your data and our honest take.
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