Klaviyo deliverability best practices: Ensuring emails reach Shopify customers

Email deliverability—percentage of emails reaching inbox versus spam folder—determines whether your Klaviyo campaigns succeed or fail. Campaign with 35% open rate and 4% click rate appears successful, but if 50% of emails land in spam folders, true performance is 17.5% opens and 2% clicks from half your intended audience. Poor deliverability invisibly undermines every optimization effort.

According to email deliverability research across e-commerce merchants, 25-40% of promotional emails from Shopify stores land in spam folders despite being legitimate marketing from subscribers who opted in. Primary causes: incomplete authentication (60% of issues), poor engagement patterns (25%), and content triggers (15%). These are fixable technical and strategic issues, not inherent limitations.

This guide provides systematic deliverability framework for Klaviyo users: authentication setup (technical foundation), engagement management (behavioral signals), content best practices (avoiding spam triggers), and monitoring systems confirming emails reach inboxes.

Understanding email deliverability

What deliverability means

Delivery rate: Percentage of emails accepted by recipient mail servers (not bouncing). Klaviyo shows this as ""Delivered"" in campaign analytics. Healthy: 98%+. This measures technical acceptance, not inbox placement.

Inbox placement rate (deliverability): Percentage of delivered emails reaching inbox versus spam/promotions folders. Klaviyo doesn't directly measure this—requires third-party tools or manual testing. Healthy: 95%+ inbox placement. This is true deliverability measuring whether subscribers actually see your emails.

Why deliverability problems develop

Email providers (Gmail, Outlook, Yahoo) use reputation-based filtering deciding whether emails reach inbox or spam. Reputation derives from: (1) Sender authentication (technical setup proving you're legitimate sender), (2) Engagement history (do recipients open/click your emails or ignore them?), (3) Content patterns (does email content match spam characteristics?), (4) Complaint rates (do recipients mark emails as spam?).

Poor reputation in any area triggers spam folder placement. Most Shopify stores have authentication gaps (technical setup incomplete) and engagement issues (sending to unengaged subscribers), creating deliverability problems despite being legitimate businesses with legitimate email lists.

Foundation: Email authentication setup

Why authentication matters

Authentication proves you're authorized sender for your domain. Without authentication, email providers can't verify emails claiming to be from ""yourstore.com"" actually come from you versus spammer impersonating your brand. Unauthenticated emails are spam-folder candidates by default.

Three authentication standards (all required)

SPF (Sender Policy Framework): DNS record listing which servers can send email for your domain. Tells receiving servers ""These IPs are authorized to send for yourstore.com.""

DKIM (DomainKeys Identified Mail): Cryptographic signature proving email wasn't modified in transit and comes from authorized sender. Tells receiving servers ""This email's content is verified authentic.""

DMARC (Domain-based Message Authentication): Policy telling receiving servers what to do with emails failing SPF/DKIM checks. Tells receiving servers ""If email fails authentication, quarantine it (spam folder) or reject it.""

All three work together. Missing any one significantly harms deliverability. Think of them as ID verification, signature verification, and security policy—you need all three for full authentication.

Setting up Klaviyo authentication (step-by-step)

Step 1: Access authentication settings. Klaviyo → Account → Settings → ""Email"" → ""Authentication"" section. Klaviyo provides specific DNS records you need to add to your domain.

Step 2: Copy DNS records. Klaviyo shows three sets of records: SPF record, DKIM records (usually 2-3 records), and DMARC record. Each includes ""Host/Name"" and ""Value"" fields—you'll need both for DNS configuration.

Step 3: Add records to your DNS. This happens where you registered your domain (GoDaddy, Namecheap, Google Domains, etc.) or where you manage DNS (often Cloudflare or your hosting provider). Log into DNS management, add each record Klaviyo provided. Record type: TXT for most (DKIM and SPF are TXT records), possibly CNAME for some DKIM records.

Step 4: Wait for propagation. DNS changes take 1-24 hours to propagate globally. Klaviyo checks authentication status automatically. After 24 hours, return to Klaviyo → Settings → Email → Authentication. All three (SPF, DKIM, DMARC) should show green ""Verified"" status.

Step 5: Verify completion. Send test email from Klaviyo to your personal Gmail. View email source (Gmail: click three dots → ""Show original""). Search for ""SPF: PASS,"" ""DKIM: PASS,"" ""DMARC: PASS."" All three should show PASS. If any show FAIL, authentication setup incomplete—revisit DNS records.

Common authentication problems

Problem: DKIM fails despite adding records. Solution: DKIM records are very long (200+ characters). Ensure entire value copied without truncation. Some DNS providers require removing quotes around TXT record values. Test both with and without quotes.

Problem: SPF fails for subdomain. Solution: If sending from ""mail.yourstore.com"" instead of ""yourstore.com,"" SPF record must exist for subdomain specifically. Add SPF record to subdomain in DNS.

Problem: DMARC not showing verified. Solution: DMARC requires both SPF and DKIM passing first. Verify those two show green in Klaviyo before expecting DMARC verification. DMARC can take 48 hours to verify after SPF/DKIM pass.

Engagement management (behavioral signals)

Why engagement matters for deliverability

Email providers monitor how recipients interact with your emails. High open/click rates signal valuable content (inbox delivery). Low open rates, especially with many deletes without opening, signal spam-like content (spam folder delivery). This creates feedback loop: good engagement improves deliverability, which improves engagement, which further improves deliverability.

Practice 1: Suppress unengaged subscribers

The problem: Subscriber hasn't opened any email in 180 days. Continuing to send creates negative engagement signals (unopened emails) harming reputation. Gmail notices this subscriber never opens your emails and increasingly spam-folders future sends.

The solution: Automatically suppress subscribers who haven't engaged in 180 days. Klaviyo → Lists & Segments → Create Segment → ""Engaged Subscribers"" (definition: opened or clicked in last 180 days). Send all campaigns to ""Engaged Subscribers"" segment, not full list.

Before suppressing long-term unengaged: Send one-time win-back campaign (""We miss you: 25% off"") to subscribers unengaged 180+ days. This gives final opportunity to re-engage. Subscribers who open win-back campaign return to engaged segment automatically. Subscribers who ignore win-back campaign (majority) confirm they're truly unengaged—suppress from future campaigns permanently.

Expected impact: Suppressing unengaged typically removes 20-40% of list but improves inbox placement 10-20 percentage points. Total email revenue often increases despite smaller audience—better deliverability to engaged subscribers generates more revenue than poor deliverability to full list.

Practice 2: Gradual list warmup for new accounts

The problem: New Klaviyo account with 10,000 imported subscribers sends first campaign to entire list. Email providers see new sender suddenly sending 10,000 emails—spam pattern. Result: immediate spam folder placement despite legitimate list.

The solution: 30-day warmup schedule. Send small volumes initially, gradually increasing as reputation builds. Week 1: Send to 500 most engaged (opened emails recently at previous ESP). Week 2: Send to 1,500 most engaged. Week 3: Send to 4,000 most engaged. Week 4: Send to 10,000 (full list). This demonstrates to email providers that you're legitimate sender with engaged audience.

When warmup required: New Klaviyo account (first 60 days), new sending domain, list imported from different ESP, or after sending hiatus of 90+ days. Existing Klaviyo users with established sending history don't need warmup for regular campaigns.

Practice 3: Maintain consistent sending cadence

The problem: Store sends 8 campaigns in November (holiday season), then 1 campaign in December, 0 in January, 2 in February. Erratic sending patterns raise spam suspicion—legitimate businesses have consistent communication rhythms.

The solution: Establish sustainable sending frequency and maintain it: 1 campaign weekly (52 annually), 2 campaigns weekly (104 annually), or 1 campaign every 2 weeks (26 annually). Consistency matters more than specific frequency. Sending 1/week for 50 weeks is better for deliverability than sending 3/week for 10 weeks then nothing for 40 weeks.

Content best practices (avoiding spam triggers)

Subject line spam triggers

Avoid: ALL CAPS (""BUY NOW AND SAVE""), excessive punctuation (""Sale!!! 70% Off!!!""), spam words (""FREE,"" ""Guaranteed,"" ""No risk,"" ""Act now""), misleading claims (""You've won"" when they haven't), and excessive emoji (""🔥🔥🔥 HOT SALE 🔥🔥🔥"").

Use instead: Sentence case (""Weekend sale: 25% off dresses""), moderate punctuation (single exclamation point acceptable), descriptive words (""25% off"" instead of ""FREE""), truthful claims, and 0-2 emoji maximum if any.

Why: Spam filters trained on billions of spam emails recognize these patterns. Subject line ""FREE VIAGRA NO PRESCRIPTION"" is obvious spam. But ""FREE SHIPPING 70% OFF BUY NOW"" triggers similar filters despite being legitimate sale announcement. Keep subject lines conversational and specific.

Body content spam triggers

Avoid: Image-only emails (no text content), hidden text (white text on white background), excessive links (10+ links in single email), shortened URLs (bit.ly, tinyurl), all-red text (screaming), forms or JavaScript (security risk), and attachments.

Use instead: Text-to-image ratio 60:40 or better (more text than images), visible text matching image content, 3-7 links maximum, full URLs showing destination domain (""yourstore.com/products/item""), normal color text (black or brand colors), no forms (link to landing page instead), and no attachments (link to download instead).

Technical content issues

Broken links: Links to 404 pages or non-existent products harm reputation. Before sending campaign, click every link verifying destination exists and loads correctly. Klaviyo doesn't check link validity automatically.

Missing unsubscribe link: CAN-SPAM law requires visible unsubscribe link in all commercial emails. Klaviyo templates include this automatically, but custom-coded emails might omit it. Missing unsubscribe link violates law and triggers spam filters.

Mismatched from/reply-to addresses: Email from ""noreply@yourstore.com"" with reply-to ""someone@differentdomain.com"" raises authentication concerns. Use same domain for both, preferably same address (""hello@yourstore.com"" for both from and reply-to).

List quality management

Only email confirmed opt-ins

Never do: Buy email lists (immediate spam folder), scrape emails from websites (illegal and spam folder), add customers to marketing emails without permission (violation of CAN-SPAM and often GDPR), or import contact lists from other sources (business cards, networking events) without explicit email permission.

Always do: Collect emails through signup forms with clear opt-in (""Subscribe to our newsletter""), double opt-in for EU subscribers (email confirmation required), transactional permission separate from marketing (order confirmation emails don't permit marketing emails), and re-permission old lists (if list is 2+ years old without engagement, send re-permission campaign before regular marketing).

Remove hard bounces immediately

What bounces are: Hard bounce: email address doesn't exist or is invalid (""user@domain.com"" where user account closed). Soft bounce: temporary issue (inbox full, server temporarily down). Klaviyo tracks both automatically.

Why bounces harm deliverability: High bounce rates signal poor list quality—spammers have high bounces from invalid addresses. Legitimate businesses should have under 2% bounce rates.

What Klaviyo does automatically: Klaviyo suppresses hard bounces after first bounce—won't send to that address again. Klaviyo attempts soft bounces 3-4 times before suppressing. This automatic handling protects your reputation.

What you should do: Review bounce reports quarterly (Klaviyo → Lists & Segments → Select list → ""Growth"" tab → ""Bounced"" filter). If bounce rate exceeds 3%, investigate how addresses entered your list—signup form validation might be weak, or source of imports might be low quality.

Honor unsubscribes and complaints instantly

Unsubscribes: Klaviyo automatically suppresses unsubscribed addresses within seconds. Never manually override this or attempt to re-add unsubscribed addresses—violates CAN-SPAM law and harms reputation severely.

Spam complaints: When recipient marks your email as spam (Gmail ""Report spam"" button), email provider notifies Klaviyo via feedback loop. Klaviyo automatically suppresses these addresses. Even one spam complaint per 1,000 emails harms reputation. Above 0.1% complaint rate (1 per 1,000) causes significant deliverability problems.

Monitoring deliverability

Manual inbox testing

Once monthly, send test campaign to personal email addresses across providers: Gmail, Outlook, Yahoo, Apple Mail. Check where emails land: inbox, promotions tab (Gmail), or spam folder. If any land in spam, deliverability problem exists requiring investigation.

How to test: Create test segment in Klaviyo with your test email addresses. Send upcoming campaign to test segment 24 hours before real send. Review inbox placement across all test accounts. If inbox placement is good across all providers, proceed with real campaign. If any provider spam-folders, investigate authentication, content, or engagement issues before sending.

Deliverability monitoring tools

Mail-Tester (mail-tester.com): Free tool scoring email deliverability. Send test email to address Mail-Tester provides, get score (10/10 is perfect). Identifies specific issues: authentication problems, content spam triggers, blacklist status.

GlockApps or 250ok (paid tools): Comprehensive deliverability monitoring testing inbox placement across 20+ email providers simultaneously, tracking authentication, blacklist monitoring, and engagement metrics. Cost: $50-200/month. Justifiable for stores sending 100k+ emails monthly or experiencing deliverability problems.

Klaviyo metrics indicating deliverability problems

Declining open rates without content changes: Open rates dropping 20%+ over 2-3 months despite consistent content signals worsening deliverability (more emails landing in spam/promotions folders where open rates are lower).

Rising spam complaint rates: Klaviyo → Analytics → Email Performance → ""Spam complaints."" Above 0.1% (1 per 1,000 emails) indicates deliverability risk. Investigate why recipients marking as spam: irrelevant content? Unclear opt-in? Too frequent sending?

Bounce rate above 3%: Klaviyo → Campaign analytics → ""Bounced."" Above 3% suggests list quality issues (old addresses, poor validation). Clean list by removing hard bounces and suppressing unengaged.

Fixing deliverability problems

Problem: Authentication failing

Symptom: SPF, DKIM, or DMARC showing ""Not verified"" or ""Failed"" in Klaviyo settings.

Solution: Review DNS records. Compare Klaviyo's provided values to what's actually in your DNS (use DNS checker tool like ""MxToolbox""). Ensure records exactly match Klaviyo's values. Common issues: typos, incomplete values (truncated), or records added to wrong subdomain. After corrections, allow 24-48 hours for verification.

Problem: Spam folder placement

Symptom: Manual testing shows emails consistently landing in spam across multiple providers (Gmail, Outlook, Yahoo).

Solution checklist: (1) Verify authentication passing (all three: SPF, DKIM, DMARC), (2) Review subject line and content for spam triggers using Mail-Tester, (3) Check if sending domain is blacklisted (MxToolbox blacklist check), (4) Suppress unengaged subscribers (haven't opened in 180+ days), (5) Reduce sending frequency if sending 8+ campaigns monthly (list fatigue increases spam complaints).

Problem: Low engagement driving poor deliverability

Symptom: Open rates declining steadily, unsubscribe rates rising, spam complaints increasing.

Solution: Re-engagement campaign followed by suppression. Create segment: ""Unengaged"" (opened zero emails in last 180 days). Send single re-engagement campaign offering strong incentive (""We miss you: 30% off""). Subscribers who open this campaign return to engaged segment. Subscribers who ignore (majority) get permanently suppressed from campaigns. This removes negative engagement signals, allowing reputation to recover over 30-60 days.

Deliverability improvement timeline

Immediate fixes (0-7 days)

Set up authentication if missing (1 day setup, 1-2 days DNS propagation). Create ""engaged subscribers"" segment and switch all campaigns to it (immediate). Test emails manually across providers identifying immediate issues (1 day).

Short-term improvements (7-30 days)

Run re-engagement campaign to unengaged subscribers, then suppress non-responders (1 week campaign, then permanent suppression). Review and fix content spam triggers (subject lines, excessive links, image-only emails). Establish consistent sending cadence (weekly or bi-weekly).

Long-term reputation building (30-90 days)

After implementing authentication and engagement management, deliverability improves gradually as email providers observe consistent positive signals. Inbox placement improving 10-15 percentage points monthly is typical. After 90 days of clean practices, most stores achieve 95%+ inbox placement.

Klaviyo Deliverability Best Practices

Email deliverability requires three foundations: (1) Complete authentication (SPF, DKIM, DMARC all verified in Klaviyo settings), (2) Engagement management (suppressing subscribers unengaged 180+ days, sending to ""engaged subscribers"" segment only), (3) Content best practices (avoiding spam triggers in subject lines and body).

Priority actions: If authentication not set up, complete within 48 hours (biggest deliverability impact). If sending to full list including unengaged, create ""engaged subscribers"" segment and switch immediately (second-biggest impact). If experiencing spam folder issues, use Mail-Tester identifying specific content or authentication problems.

Expected outcomes: Proper authentication improves inbox placement 15-30 percentage points. Suppressing unengaged improves inbox placement additional 10-20 points. Combined: 95%+ inbox placement achievable for legitimate Shopify stores following these practices.

Ongoing maintenance: Monthly manual inbox testing (send test campaign to Gmail, Outlook, Yahoo, verify inbox placement). Quarterly list health review (bounce rates, unsubscribe rates, engaged percentage). Authentication verification after any DNS changes. These maintenance tasks prevent gradual deliverability decay.