Why your emails go to spam and how to fix it

If your store's emails go to spam, the cause is almost always one of three things: your domain is not authenticated, you send from a shared domain whose reputation is not yours, or you keep emailing people who stopped reading you. Inbox providers judge you on who you are and on how your recipients react. The words in the subject line come much later.

This guide lists the causes in the order we check them in a store that sends marketing from Klaviyo or Shopify, how to confirm each one and what to do about it.

Start with the symptom, not the theory

Most "spam" problems leave a clear trace. Find yours in the table before changing anything.

Cause 1. Your domain is not authenticated

SPF, DKIM and DMARC are three DNS records that prove an email really comes from your domain. Google requires SPF or DKIM from every sender. If you send more than 5,000 messages a day to Gmail addresses, you also need SPF and DKIM together, a DMARC record, and your From domain aligned with SPF or DKIM. Yahoo asks bulk senders for the same: SPF, DKIM and a valid DMARC policy of at least p=none that passes.

How to check it: run your domain through our email deliverability checker. It reads your public DNS and tells you which record is missing or misconfigured in a few seconds, without access to your account.

What we see most often in stores: DMARC missing entirely, or two SPF records on the same domain after switching tools. The SPF standard does not allow more than one SPF record per domain, so the fix is to merge them, not to add a third.

Cause 2. You send from a shared domain

By default, Klaviyo sends from a shared domain and shared IPs. You can spot it because recipients see "via klaviyomail.com" next to your address. Klaviyo's help centre is clear about the trade-off: on a shared domain, other Klaviyo customers use the same sending domain, so you can inherit its reputation.

A branded sending domain moves that reputation onto your own domain. It removes the "via" line, lets your DMARC do its job and limits the damage other senders can do to you. Klaviyo also treats it as part of meeting the bulk sender requirements of Google and Yahoo.

Our criterion is simple. Any store that sends campaigns every week should have its own sending domain from day one. It takes a few DNS records and it is the base for everything else in this guide.

Cause 3. You keep emailing people who stopped reading

This is the slow cause, and in stores with a list a few years old it is the most common one. Providers watch how recipients treat your emails. If a large part of the list never opens or clicks, your emails start drifting towards spam for everyone, including your best customers.

Klaviyo's troubleshooting guide says it directly: sending to dormant subscribers again and again, without a sunset policy, can lower your sending reputation. Yahoo says the same: sending email to users who are not reading it will harm your delivery metrics.

How we fix it:

1. Campaigns go to an engaged segment, not to the whole list. Define it by clicks and purchases first. Opens alone are not reliable: Apple Mail Privacy Protection loads images before anyone reads, so Klaviyo marks those opens with the Apple Privacy Open property. If you use opens, add "where Apple Privacy Open equals False".
2. A sunset flow for people with no opens or clicks in 90 days. Two emails over seven days, the first asking if they want to stay, the second confirming the goodbye. No discount. If they interact, they go back to the active list. If not, they are suppressed.
3. Never-engaged profiles out first. Klaviyo recommends suppressing those who have never opened, clicked or purchased when emails start landing in spam.

Cause 4. Too many spam complaints

Every time someone marks your email as spam, providers count it against you. Google asks senders to keep the spam rate reported in Postmaster Tools below 0.10% and to never reach 0.30%. Yahoo also sets its limit at 0.3%. Klaviyo's own guidance goes further and suggests aiming under 0.01%.

How to check it: set up Google Postmaster Tools for your domain. Klaviyo itself notes that most complaints are never reported back to the sender, and Postmaster shows you the Gmail figure.

Complaints usually come from three places: people who did not expect your emails, people who receive too many, and people who cannot find how to unsubscribe. So the fixes are in that order. Say clearly at signup what you will send and how often. Send campaigns to engaged segments. Put the unsubscribe link where it is easy to find.

Cause 5. Unsubscribing is hard

Someone who cannot unsubscribe in one tap presses "report spam" instead. Google requires one-click unsubscribe for marketing messages from bulk senders, and Yahoo asks you to honor unsubscribes within 2 days.

In Klaviyo the technical part is already covered: it adds the one-click unsubscribe header to every email automatically. What you control is the visible link in the email. Klaviyo requires one in every email, and its advice on complaints is to make it easy to find and easy to tap on mobile. A grey link in 8px text at the bottom of a long email works against you.

Cause 6. A sudden spike in volume

Shopify's help centre puts it plainly: sudden changes in volume are the most common cause of blocks and delays, even for trusted senders. Providers may defer, throttle or block messages when they see a spike, and Google warns against sudden volume spikes if you have no history of sending large volumes.

This is why so many stores land in spam during Black Friday week. They send to the whole list, dormant profiles included, several times in a few days. Shopify's advice is to raise your volume by 20% to 30% a week until you reach the target. If you are planning that week now, our Black Friday email plan shows how we spread the sends.

Cause 7. A purchased or very old list

Yahoo is explicit: do not purchase mailing lists, and do not subscribe people with a checkbox that is already ticked. Bought lists bring addresses that never asked for your emails, addresses that no longer exist and, often, spam traps. One send to that list can undo months of good reputation.

The same applies to an old customer list you never emailed. If those people have not heard from you in years, write to them as if they were new: a small, careful send to recent buyers first, never the whole file at once.

Cause 8. The content itself

It comes last because it is rarely the root cause in a store with authentication and a clean list. Klaviyo's troubleshooting guide still lists a few things to avoid: subject lines in all caps, lots of symbols and emails that are a single image with no text. Our rule is that every email carries real text, one main message and one call to action. It reads better and it filters better.

If you have gone through the eight causes and your emails still land in spam, the problem is usually in your account data: segments, frequency and complaint history. That is what we review in a 30-minute call.

Sources

Checked on October 5, 2026.

• Google: email sender guidelines
• Yahoo: sender best practices
• Shopify: email volume consistency
• Klaviyo: branded vs. shared sending domains
• Klaviyo: troubleshooting why emails go to spam
• Klaviyo: how to reduce spam complaint rates
• Klaviyo: how to clean your email list
• Klaviyo: identifying Mail Privacy Protection opens
• Klaviyo: adding an unsubscribe link
• RFC 7208, the SPF standard, section 3.2