Your email marketing is only as effective as the percentage of your emails that actually reach the inbox. Deliverability — the ability of your emails to land in the primary inbox rather than spam or Promotions — is not a one-time setup task but an ongoing discipline. Shopify store owners running Klaviyo or Omnisend can have technically perfect templates and strong offers and still see campaigns fail to reach subscribers if their sender reputation is damaged. This guide covers the technical foundations (SPF, DKIM, DMARC), the content practices that keep you out of spam filters, how to warm up a new sending domain, list hygiene routines, and how to check your sender score with free tools so you can identify problems before they become crises.
Why Emails Land in Spam
Inbox providers use dozens of signals to classify incoming email. The most impactful are: engagement rate (what percentage of recipients open and click your emails), spam complaint rate (what percentage mark your email as spam — anything above 0.1% is a red flag for Gmail), bounce rate (what percentage of your sends return as undeliverable), and sender authentication (whether your domain has correctly configured SPF, DKIM, and DMARC records). Content factors play a secondary role — spam trigger words like “free,” “guaranteed,” and “act now” are noticed, but a strong sender reputation can often overcome borderline content. Conversely, a poor reputation will cause even clean, well-written emails to be filtered. Reputation is the foundation; content is the polish.
SPF, DKIM, and DMARC Setup
These three DNS records prove to inbox providers that emails sent from your domain are authorised. SPF (Sender Policy Framework) lists the servers permitted to send email on behalf of your domain. DKIM (DomainKeys Identified Mail) adds a cryptographic signature to every email that receiving servers use to verify authenticity. DMARC (Domain-based Message Authentication, Reporting, and Conformance) tells inbox providers what to do with emails that fail SPF or DKIM checks, and sends you reports on authentication failures. Setting up all three reduces the probability of your emails being spoofed, and Gmail and Yahoo both made DKIM and DMARC mandatory for bulk senders in 2024. Your email platform — Klaviyo, Omnisend — provides the DNS values to add to your domain’s DNS settings. Use MXToolbox to verify all three records are correctly configured after adding them.
Warming Up a New Sending Domain
If you are starting a new sending domain or switching email providers, you cannot immediately send to your full list. Inbox providers have no reputation history for your new domain and will treat high-volume sends from an unknown sender with suspicion. A domain warm-up involves gradually increasing send volume over four to six weeks: start with your most engaged subscribers (opened or clicked in the last 30 days), send small batches of 500–1,000 per day in week one, doubling every few days as engagement signals build. Most email platforms including Klaviyo have built-in dedicated domain warm-up tools that automate this process. Skipping warm-up and sending a full campaign on day one is one of the most common causes of catastrophic deliverability crashes for new Shopify brands.
List Hygiene and Re-Engagement
A healthy email list has more value when it is smaller and engaged than when it is large and stale. Run list hygiene on a quarterly basis: suppress hard bounces (email addresses that returned a permanent delivery failure) immediately, soft bounces (temporary failures) after three consecutive bounces, and unengaged subscribers (no open or click in 120 days) after a re-engagement attempt. Before suppressing unengaged subscribers, run a 2-email re-engagement campaign: Email 1 with subject “Are you still interested in hearing from us?” and Email 2 five days later offering a final incentive. Anyone who does not engage with both emails should be suppressed. The short-term list size reduction is always worth it for the deliverability improvement. Check your sender score using SenderScore or Google Postmaster Tools (free, and essential for stores with a large Gmail subscriber base). A score above 80 is healthy; below 70 signals active problems that need investigation. OneOnic audits Shopify email deliverability setups and resolves authentication and hygiene issues for growing brands.
Frequently Asked Questions
How do I know if my Shopify emails are landing in Gmail’s Promotions tab?
Send a test email from your Klaviyo or Omnisend account to a Gmail address and check which tab it arrives in. The Promotions tab is not the same as spam — emails there are still delivered and read, just with lower urgency. To reduce Promotions tab placement, use a more personal from-name (your name rather than your brand name), reduce the image-to-text ratio, and encourage subscribers to move your emails to Primary by asking them in your welcome email.
What text-to-image ratio should I use in Shopify email templates?
Aim for a ratio of at least 60% text to 40% images. Spam filters treat image-heavy emails with low text content as suspicious because spammers historically used images to embed text that filters could not read. Every image should have descriptive alt text. Avoid sending emails that are a single large image with no text — these score poorly in spam filters and are inaccessible to subscribers who have images turned off by default in their email client.
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