Why Email Deliverability Is Your Most Important Klaviyo Metric
You can have the best subject lines, flows, and offers in the world — but if your emails land in spam, none of it matters. Email deliverability is the foundation everything else is built on.
Klaviyo gives you more control over deliverability than almost any other platform, but you need to use that control correctly. This guide covers everything you need to maintain inbox placement and protect your sender reputation.
Understanding Email Deliverability
Deliverability refers to the ability of your emails to reach subscribers’ inboxes (rather than spam folders or being blocked entirely). It’s determined by a combination of technical factors, behavioral signals, and your sending reputation.
- Inbox placement rate: percentage of sent emails that reach the inbox (not spam)
- Delivery rate: percentage that weren’t bounced or blocked
- Spam complaint rate: percentage of recipients who mark your email as spam
- Open rate: used by mailbox providers as an engagement signal
Technical Authentication: The Non-Negotiables
Before you send a single campaign, verify these technical settings in your domain’s DNS:
- SPF (Sender Policy Framework): authorizes Klaviyo to send on behalf of your domain
- DKIM (DomainKeys Identified Mail): adds a digital signature to verify email authenticity
- DMARC (Domain-based Message Authentication): tells providers what to do with unauthenticated mail
- Custom sending domain in Klaviyo: use yourname@yourdomain.com, never a free Gmail or Yahoo address
Klaviyo provides step-by-step instructions for configuring all of these in Account → Settings → Email → Sending Domains. Don’t skip this — it’s the most impactful technical change you can make.
List Hygiene: Clean Your List Regularly
Sending to invalid, inactive, or unengaged addresses destroys your reputation. Gmail, Yahoo, and Outlook track engagement signals — if your open rates drop too low, they start routing you to spam.
- Remove hard bounces immediately (Klaviyo does this automatically)
- Suppress soft bounces after 3–5 failures
- Suppress contacts who haven’t opened in 180+ days before sending to them
- Never buy email lists — they contain spam traps that blacklist your domain
- Run a re-engagement campaign before suppressing inactive subscribers
Warming Up a New Sending Domain
If you’re sending from a new domain or a new IP, you must warm it up gradually. Mailbox providers don’t trust new senders — you need to build reputation over time.
- Week 1: Send to your most engaged subscribers only (opened in last 30 days)
- Week 2: Expand to opened in last 60 days
- Week 3: Opened in last 90 days
- Week 4+: Gradually expand to your full list
- Monitor spam complaint rates — keep below 0.08% at all times
Segmentation for Deliverability
One of the best deliverability strategies is sending only to engaged subscribers. In Klaviyo, create an “engaged” segment:
- Opened email at least once in the last 90 days, OR
- Clicked email at least once in the last 120 days, OR
- Placed an order in the last 180 days
Send campaigns only to this segment. Your open rates go up, mailbox providers see high engagement, and your inbox placement improves over time.
Monitoring Your Deliverability in Klaviyo
Klaviyo’s Deliverability Hub (under Analytics → Deliverability) shows:
- Spam complaint rate by domain (Gmail, Yahoo, etc.)
- Bounce rates and bounce types
- Open rate trends over time
- Unsubscribe trends
Set up email alerts in Klaviyo for high bounce rates or spam complaints. Catching issues early prevents lasting damage to your sender reputation.
Common Deliverability Mistakes to Avoid
- Sending too many emails too quickly after a long pause
- Using spam-trigger words in subject lines (“FREE!!!”, “Act now”, “Guaranteed”)
- Embedding too many images with no text (spam filters distrust image-heavy emails)
- Using URL shorteners (bit.ly, etc.) in emails — major spam red flag
- Neglecting to suppress bounces, complaints, and unsubscribes
- Sending campaigns to your entire list without segmenting for engagement
Struggling with spam folder placement or low open rates? A Klaviyo deliverability specialist can audit your setup and fix issues before they compound.