Email deliverability is the silent killer of Shopify email marketing. You can write the perfect subject line, design the most beautiful template, and craft an offer your customers cannot refuse — but if your emails are landing in spam folders or promotions tabs, none of it matters. You are essentially sending love letters to a void.
What’s in This Article
Most Shopify store owners have no idea what their deliverability looks like. They check open rates and assume everything is fine. But open rates only measure the emails that actually reached the inbox. If 20% of your emails are hitting spam, your reported 25% open rate is actually masking a much bigger problem — your true reach is significantly lower than you think.
The rules tightened sharply in 2024, when Google and Yahoo brought in strict new requirements for bulk senders. If you are sending marketing emails to Gmail or Yahoo addresses (which together represent over 60% of Australian email users), you need to meet specific authentication and engagement requirements or risk having your emails blocked entirely.
The Three Pillars of Email Deliverability
Email deliverability comes down to three factors: authentication (proving you are who you say you are), reputation (proving you are a trustworthy sender), and engagement (proving people actually want your emails). Neglect any one of these and your deliverability will suffer.
Pillar 1: Authentication. Email authentication protocols prove to inbox providers that your emails are legitimately from your domain and have not been spoofed or tampered with. Three protocols matter: SPF (Sender Policy Framework) tells receiving servers which mail servers are authorised to send email on behalf of your domain. DKIM (DomainKeys Identified Mail) adds a digital signature to your emails that verifies they have not been altered in transit. DMARC (Domain-based Message Authentication, Reporting and Conformance) tells receiving servers what to do with emails that fail SPF or DKIM checks.
If you are using Klaviyo or Omnisend with a custom sending domain (which you should be), these platforms guide you through setting up all three protocols. It involves adding DNS records to your domain — a one-time setup that takes 15-30 minutes. If you have not done this, stop reading and go do it now. Without proper authentication, your emails are far more likely to hit spam.
Building and Protecting Sender Reputation
Pillar 2: Sender reputation. Every email you send either builds or damages your sender reputation — a score that inbox providers use to decide whether your emails deserve the inbox or the spam folder. Think of it like a credit score for email.
Clean your list regularly. Dead email addresses, spam traps, and disengaged subscribers all damage your sender reputation. Run a list cleaning at least every 90 days: remove hard bounces immediately, suppress soft bounces after 3 consecutive failures, and segment out subscribers who have not opened or clicked in 180 days. Tools like ZeroBounce or NeverBounce can identify invalid addresses before you send to them.
Warm up new sending domains. If you are switching to a new sending domain or setting up a custom domain for the first time, do not blast your entire list on day one. Start by sending only to your most engaged subscribers (opened in the last 30 days) for the first 2 weeks. Gradually increase volume over 4-6 weeks. This “warm-up” process teaches inbox providers that your domain sends emails people want to receive.
Monitor your bounce and complaint rates. Your hard bounce rate should stay below 0.5% per send. Your spam complaint rate should stay below 0.1% (Google’s new threshold). Above these numbers, you are actively damaging your reputation. If you see spikes in either metric, immediately investigate: Are you sending to stale addresses? Did you import an unverified list? Is your content triggering spam filters?
Engagement: The Metric That Rules Everything
Pillar 3: Subscriber engagement. Gmail, Yahoo, and other providers heavily weight engagement signals when deciding inbox placement. If people consistently open, click, and reply to your emails, your deliverability improves. If they consistently ignore, delete without opening, or mark as spam, it deteriorates.
Send to engaged segments first. This is the single most impactful deliverability tactic. When sending campaigns, always send first (or exclusively) to your engaged segment — subscribers who have opened or clicked in the last 90 days. These subscribers are most likely to interact with your email, which sends positive signals to inbox providers and improves placement for subsequent sends.
Sunset unengaged subscribers. If a subscriber has not opened a single email in 180 days, they are either not seeing your emails (deliverability issue) or not interested (engagement issue). Run a re-engagement campaign with a compelling subject line and clear value proposition. Those who still do not engage after 2-3 attempts should be suppressed from future sends. Yes, your list size will shrink — but your deliverability, open rates, and revenue will improve.
Optimise send frequency. Over-sending is one of the fastest ways to kill engagement and deliverability. For most Shopify stores, 2-3 campaigns per week is the sweet spot. Beyond that, you start to see diminishing returns and rising unsubscribe rates. Monitor your unsubscribe rate per campaign — if it exceeds 0.3%, you are either sending too often or your content is not relevant enough.
Technical Fixes That Improve Inbox Placement
- Use a custom sending domain. Sending from “your-store.klaviyomail.com” shares reputation with every other Klaviyo user. A custom sending domain (email.yourbrand.com.au) gives you your own reputation that you control. Set this up in your email platform settings — it requires adding CNAME records to your DNS.
- Avoid spam trigger words. Words like “free,” “guaranteed,” “act now,” “limited time,” and excessive exclamation marks can trigger spam filters. Write naturally and focus on value instead of hype. Your subject lines should sound like a person wrote them, not a used car salesman.
- Maintain a healthy text-to-image ratio. Emails that are 100% images with no text are a major spam trigger. Aim for at least 60% text, 40% images. Always include a text version of your email (most platforms do this automatically).
- Include a clear unsubscribe link. This is legally required in Australia under the Spam Act 2003, but it also helps deliverability. Making it easy to unsubscribe is better than having frustrated subscribers mark you as spam. An unsubscribe is neutral for your reputation; a spam complaint is devastating.
Monitoring Deliverability: The Dashboard You Need
Check these metrics weekly to catch deliverability issues before they become crises. Open rate trending down over 4+ weeks is the earliest warning sign. Hard bounce rate per campaign should stay under 0.5%. Spam complaint rate should remain under 0.1%. List growth rate minus unsubscribes tells you if your list is healthy. And delivery rate (emails accepted by receiving servers) should be above 98%.
The Gmail and Yahoo Sender Rules That Changed Everything
In February 2024, Gmail and Yahoo stopped treating authentication as a nice-to-have. If you send more than 5,000 messages a day to Gmail addresses, you now have to meet a hard set of requirements or your mail gets rejected outright. Most Aussie Shopify brands are under that threshold, but the enforcement is drifting downward and the smart move is to meet the bulk sender bar regardless of your volume.
There are four requirements and none of them are optional. You need SPF and DKIM both passing on every send. You need a DMARC record published, even if the policy is set to p=none while you monitor. You need one-click unsubscribe implemented as a List-Unsubscribe header, not just a link buried in your footer. And you need to keep your spam complaint rate below 0.3% measured in Google Postmaster Tools, with 0.1% being the level you should actually be aiming for.
The complaint rate is where most brands get caught out. A 0.3% complaint rate sounds tiny until you do the arithmetic: on a 20,000-person send, that is 60 people hitting the spam button. One aggressive Black Friday campaign to a cold segment can blow past that in a single morning, and the damage does not reset the next day. Gmail weights recent behaviour heavily, so a bad send in November can suppress your inbox placement right through to January.
Klaviyo and Omnisend both handle List-Unsubscribe headers automatically on their shared sending infrastructure, so if you are on either platform that box is already ticked. What they cannot do for you is publish your DMARC record or keep your complaint rate down. That part is yours.
Warming a New Sending Domain Without Burning It
If you are moving from Shopify Email to Klaviyo, switching your sending domain, or launching a second brand, you are effectively a stranger to every inbox provider on day one. A brand new domain has no reputation, and no reputation is treated with more suspicion than a mediocre one. Send 15,000 emails on your first day from a fresh domain and a meaningful share will land in spam no matter how good your content is.
The fix is a warm-up schedule, and it is less painful than it sounds. Start at roughly 500 sends on day one, and only to your most engaged people: 30-day openers and recent purchasers. Roughly double the volume every second day, so day three is 1,000, day five is 2,000, day seven is 4,000, and so on. A full warm-up to a list of 50,000 takes about three weeks. Skipping it costs you months.
Two rules make the difference. Send your warm-up campaigns at consistent times rather than in irregular bursts, because inbox providers read volume spikes as a compromise signal. And watch your open rate as you scale: if it drops below about 25% on a segment that normally opens at 40%, hold the volume flat for two more sends before you increase again. You are proving to Gmail that people want your mail. That takes repetition, not speed.
Keep transactional mail on a separate subdomain from marketing mail. Order confirmations open at 60% or better and shipping notifications at 50% or better, and mixing that traffic with promotional sends means one bad campaign can drag down the reputation of the emails your customers genuinely need to receive. If your order confirmations start landing in spam, you have a support problem on top of a marketing problem.
The Sunset Flow That Protects Your Sender Score
Every list has a dead tail. People who subscribed for a discount code two years ago, never opened again, and now sit there quietly dragging your engagement rate down. Most founders keep mailing them because a bigger list number feels like an asset. It is not. It is a liability, because inbox providers judge you on the percentage of recipients who engage, not the raw count who receive.
Build a sunset flow in Klaviyo and let it run permanently. Trigger it when someone has not opened or clicked in 90 days but is still receiving campaigns. Send a three-email sequence: a straight “are you still interested?” with your best offer, a second email four days later with a genuinely different angle, and a final “we are removing you unless you tell us otherwise” a week after that. Anyone who engages goes back into your active segment. Anyone who does not gets suppressed.
Expect roughly 5-10% of a lapsed segment to re-engage. That is the win people focus on, but it is the smaller of the two. The bigger win is what happens to the 90% you suppress: your list shrinks, your open rate climbs, and because inbox placement follows engagement, the mail you send to your good customers starts landing better. Brands running a disciplined sunset flow typically see open rates lift 8-15 percentage points within two months of the first big suppression.
Suppress rather than delete. A suppressed profile keeps its purchase history and stays available for paid audience matching, so you can still reach those people through Meta or Google without touching your sender reputation. Deleting them throws away data you paid to acquire.
Your Deliverability Diagnostic: 8 Checks to Run This Week
You do not need a consultant to find out whether you have a problem. Work through these eight checks in about an hour and you will know exactly where you stand.
- Run your domain through MXToolbox. Check SPF, DKIM and DMARC all resolve and that you have exactly one SPF record. Two SPF records is a hard fail and it is one of the most common misconfigurations we find.
- Verify your domain in Google Postmaster Tools. It is free, takes ten minutes, and it is the only place you see your actual Gmail spam complaint rate and domain reputation rather than guessing from open rates.
- Check your sending domain is a subdomain of your store domain. Sending from
send.yourbrand.com.aukeeps marketing reputation separate from your root domain. - Look at open rate by inbox provider. Klaviyo lets you segment by email domain. If Gmail opens are 15 points below Outlook, you have a Gmail-specific reputation issue, not a content issue.
- Check your unsubscribe link works in one click. Forcing people through a preference centre to unsubscribe drives them to the spam button instead, and a spam complaint hurts you roughly 100 times more than an unsubscribe.
- Audit your signup sources. Any list you bought, scraped, imported from an old platform, or collected via a giveaway with no purchase intent is actively poisoning your reputation. Suppress it.
- Confirm double opt-in on your popup. It costs you roughly 20-30% of raw signups and pays that back in engagement quality within a quarter.
- Send a seed test. Set up test addresses on Gmail, Outlook and Yahoo, send yourself the next campaign, and see with your own eyes which tab it lands in.
If more than two of those come back bad, stop sending campaigns until they are fixed. Every send you make with broken authentication or a poisoned list makes the recovery longer.
Deliverability is a Promotion problem with a Platform root cause, which is why it sits awkwardly between your marketer and your developer and often gets owned by neither. It is also the cheapest revenue in your business: fixing authentication and list hygiene costs you a morning and lifts every campaign you send afterwards. Once it is right, the work shifts to what you actually send, which is where your core Klaviyo flows and smarter segmentation start compounding. And if you are collecting addresses through popups and giveaways, make sure your consent process actually meets the Spam Act before you scale the list.
Deliverability Is the Foundation of Email Revenue
You can have the best email strategy in the world, but if your emails do not reach the inbox, it is all wasted effort. Authentication, reputation, and engagement work together to determine whether your emails get seen or get buried. Fix these fundamentals first, then focus on optimising content and timing. A 10% improvement in deliverability can translate to a 10% increase in email revenue — with zero extra effort on the content side.
Inside the eCommerce Circle, email deliverability is one of the first things we audit under our Promotion pillar. If your open rates are declining and you are not sure why, or if you have never set up proper email authentication, our coaching walks you through the technical setup and ongoing monitoring that keeps your emails in the inbox where they belong.
