Why your Shopify emails go to spam, and how to fix it

Marketing email from a Shopify store goes to spam for a small number of reasons, and each one can be checked. In order of how often they are the cause: the sending domain isn't authenticated, recipients are marking the mail as spam, addresses are bouncing, the list contains people who didn't sign up, or the volume rose faster than the domain's history supports. Work through them in that order. Changing subject lines and avoiding "spammy words" comes last, because mailbox providers decide mainly on who is sending and how recipients react.

What Gmail, Yahoo and Outlook require

Since February 2024 Gmail and Yahoo have published sender rules, and Outlook.com added its own in May 2025. They are the baseline: mail that doesn't meet them is filtered or rejected whatever it says.

The 5,000-a-day line is lower than it sounds. One campaign to a list of 6,000 Gmail addresses crosses it, and Gmail then treats the domain as a bulk sender permanently.

1. Authenticate your sending domain

Authentication tells the mailbox provider that the email really comes from your domain. Three DNS records do the work:

• SPF lists the servers allowed to send for the domain.
• DKIM signs each message, so the provider can check it wasn't changed in transit.
• DMARC tells the provider what to do when SPF and DKIM fail, and requires that one of them matches your From domain.

How to check. Send yourself a campaign at a Gmail address, open it, choose "Show original", and look for SPF: PASS, DKIM: PASS and DMARC: PASS. A fail or a missing line is your first fix.

Sending from a shared domain that belongs to your email tool, or from a free address such as yourstore@gmail.com, fails alignment by design. Send from a domain you own.

In Zalify you add the sender domain under Email settings, copy the DKIM, SPF and Return-Path records into your DNS, and verify them. The same page shows whether the domain publishes a DMARC record and gives you one to copy when it doesn't. Broadcasts can't be submitted from an unverified domain. See verifying your sender domain.

2. Bring the complaint rate down

A complaint is a recipient pressing "Report spam". It is the strongest negative signal there is, and the threshold is low: 0.3% is three people in a thousand.

How to check. Register your domain in Google Postmaster Tools and read the spam rate there. It is the figure Gmail itself uses.

What brings it down:

• Make unsubscribing easier than complaining. Put the link where people can find it, and support one-click unsubscribe.
• Send only to people who asked. Customers who bought once without ticking a marketing box did not ask.
• Send less to people who stopped reading. A subscriber who hasn't opened in six months is more likely to complain than to buy.

Zalify adds the one-click unsubscribe headers (RFC 8058) to every marketing email and its pre-send check flags a broadcast that has no working unsubscribe link. A recipient who complains is suppressed automatically, so they are never emailed again, and each broadcast's report lists who marked it as spam.

3. Stop emailing addresses that bounce

A hard bounce means the address doesn't exist. A list with many of them tells the mailbox provider that the addresses were not collected from real signups.

How to check. Look at the bounce rate of your last few campaigns. Above 2% needs attention; above 5% is a list problem.

What fixes it:

• Remove every address that hard-bounced, and never import them again.
• Don't mail a list that has sat untouched for a year without cleaning it first.
• Use double opt-in on forms that attract fake or mistyped addresses.

Zalify suppresses hard-bounced addresses automatically and skips suppressed addresses on every later send; the broadcast report shows which recipients were skipped. Lists and signup forms can be set to double opt-in.

4. Send only to people who signed up

Bought lists, scraped addresses and "everyone who ever checked out" produce complaints and bounces together, and they often contain spam traps: addresses that exist only to catch senders who didn't ask permission.

A broadcast in Zalify goes only to contacts subscribed to marketing email. Before you send, the recipient count shows how many people in the audience aren't subscribed and will be skipped. When a newly connected store's imported contacts look unlike real signups, sending is held until the list has been reviewed.

5. Raise volume gradually

Mailbox providers judge a domain by its history. A domain that sent nothing last month and 50,000 emails today looks like a compromised account or a spammer, even with perfect authentication.

What to do. Start with your most engaged subscribers, the people who bought or signed up recently, and widen the audience over two to four weeks. Keep the schedule regular: weekly sends build a history, a burst once a quarter doesn't.

Zalify enforces the gradual start for you. A new sender has a daily limit on first-time recipients, which only counts people you have never emailed before. The limit rises as your sends stay clean and is lowered after a day with too many bounces or complaints. Email to people you have already reached is not limited. More on this in how to fix a bad email sender reputation.

6. Then look at the email itself

Content matters least, but a few things do trip filters or hide your message:

• Links that use http://, or go through a public link shortener.
• An email that is one large image with little text.
• HTML so long that Gmail clips it, which hides the unsubscribe link at the bottom.
• A subject line that promises something the email doesn't contain.

Zalify's pre-send check flags http:// links, links that go nowhere, missing images, images without alt text and emails that Gmail will clip, before the broadcast is submitted.

A checklist to run today

1. Open a recent campaign in Gmail, choose "Show original", and confirm SPF, DKIM and DMARC all pass.
2. Register the domain in Google Postmaster Tools and read the spam rate.
3. Check the bounce rate of your last three campaigns.
4. Confirm that unsubscribing takes one click.
5. Send your next campaign only to people who opened or bought in the last 90 days.
6. Keep a weekly rhythm for a month, then widen the audience.

Sources

• Email sender guidelines, Google Workspace Admin Help
• Sender best practices, Yahoo Sender Hub
• Outlook's new requirements for high-volume senders, Microsoft Tech Community
• RFC 8058: Signaling one-click functionality for list email headers, IETF