Gmail and Yahoo sender requirements: the Shopify + Klaviyo checklist

For years, a Shopify store could send email from a free sending domain, ignore DNS and still reach the inbox. Not anymore. The Gmail and Yahoo sender requirements introduced in 2024, and Outlook's in 2025, turned “best practice” into rules. Miss them and your welcome series, cart flow and campaigns can land in spam or bounce outright.

This is the plain-English checklist, with the exact steps for Klaviyo and Shopify.

Who counts as a bulk sender?

Google's sender guidelines FAQ defines a bulk sender as anyone sending close to 5,000 messages or more to personal Gmail accounts within 24 hours. Three details catch stores out:

1. It counts the whole primary domain. Mail from yourbrand.com and from send.yourbrand.com adds up.
2. It's permanent. Hit the threshold once and you're treated as a bulk sender from then on.
3. It's easy to hit. A 15,000-person list where a third use Gmail crosses the line with one campaign.

Our advice: if you send campaigns at all, set things up as if you're a bulk sender. It costs an afternoon and removes the risk.

Gmail and Yahoo sender requirements: the full checklist

Sources: Gmail sender guidelines and FAQ. Yahoo's sender best practices line up closely: SPF and DKIM, a valid DMARC policy of at least p=none, From-domain alignment, complaints below 0.3%, and a working List-Unsubscribe header (one-click preferred), with opt-outs honoured within two days.

And Outlook

Microsoft followed in 2025. Its announcement for high-volume senders requires domains sending more than 5,000 emails a day to Outlook.com consumer addresses to pass SPF, DKIM and DMARC (at least p=none, aligned with SPF or DKIM), starting May 5, 2025. Non-compliant mail goes to Junk first and can later be rejected.

The Shopify + Klaviyo setup, step by step

Step 1: Check what you have now

Run your root domain through the email deliverability checker. It looks up SPF, DMARC and MX records. Note anything missing.

Step 2: Set up a branded sending domain in Klaviyo

Klaviyo's branded sending domain guide walks you through adding a subdomain (for example send.yourbrand.com) and publishing the DNS records it generates. Those records handle SPF and DKIM for mail Klaviyo sends for you. Verify, then activate it.

Tip: don't guess at your own SPF record for Klaviyo. Use the records Klaviyo gives you, and keep your root domain's SPF record for your inbox provider (Google Workspace, Microsoft 365).

Step 3: Publish a DMARC record on your root domain

Add a TXT record at _dmarc.yourbrand.com. A safe starting point:

p=none meets the Gmail, Yahoo and Outlook minimum. The rua address receives reports that show who is sending as your domain. Once reports show all legitimate mail passing, you can consider tightening the policy. Klaviyo's guide to the Google, Yahoo and Microsoft requirements covers the Klaviyo-specific details.

Step 4: Send from your own domain

Use a From address like hello@yourbrand.com, never a free Gmail or Yahoo address. Gmail's guidelines specifically warn against impersonating Gmail From headers, and a free mailbox can't pass DMARC alignment for your brand.

Step 5: Authenticate Shopify's own emails

Order confirmations and shipping updates come from Shopify, not Klaviyo. Shopify's help page on your store's sending email explains how to authenticate your domain so those messages send as your brand. Do it, or your most important transactional emails stay at risk.

Step 6: Confirm one-click unsubscribe

Open a recent campaign in Gmail, choose “Show original” and look for List-Unsubscribe and List-Unsubscribe-Post headers. Keep the visible unsubscribe link in every marketing template too. Removing it to “reduce unsubscribes” just turns unsubscribes into spam complaints.

Step 7: Set up Google Postmaster Tools

Postmaster Tools is where Gmail reports your spam rate. Verify your domain and check it weekly, and daily around big sends.

The 0.3% line: how to keep complaints down

Authentication gets you through the door. Complaints decide whether you stay in the inbox. Google says senders should keep the spam rate below 0.1% and never let it hit 0.3%. Above 0.3%, bulk senders lose eligibility for mitigation until they stay below it for 7 days in a row.

6 tactics that cut complaints

1. Send campaigns to engaged segments. Klaviyo's guidance is to exclude people who got 5+ emails without opening or clicking in 90 days from regular campaigns.
2. Confirm sign-ups. Gmail's subscription guidelines recommend that recipients confirm their address before you send subscription messages.
3. Set expectations at sign-up. Say how often you'll email. Surprises cause complaints.
4. Make leaving easy. A visible unsubscribe link costs you a subscriber. A spam complaint costs you reputation.
5. Sunset the dead weight. See how to lower your Klaviyo bill. The same cleanup saves money and protects inboxing.
6. Watch frequency. Find a cadence your list tolerates with the email frequency planner, and check copy with the spam score checker.

The 20-minute monthly deliverability routine

1. Re-run the DNS check. Records get broken when someone changes website host, inbox provider or DNS provider. Run the deliverability checker again.
2. Read Postmaster Tools. Note spam rate and domain reputation for the month. Anything trending up gets looked at before the next big send.
3. Skim DMARC reports. Look for services sending as your domain that you don't recognise, or legitimate tools (helpdesk, reviews app) that fail authentication.
4. Check engagement by inbox provider. If Gmail clicks fall while other providers hold steady, that's a reputation signal, not a content problem. (If clicks per open drop everywhere, that's the email itself: see my click to open rate benchmark guide.)
5. Refresh your engaged segment and make sure campaigns still exclude long-term unengaged profiles.
6. Review unsubscribe and complaint rates per campaign. One campaign with a spike tells you which kind of message your list dislikes. Track it in the unsubscribe rate calculator.

Twenty minutes a month is cheap insurance. Your flows, the part of email that earns money while you sleep, only work if they land in the inbox.

Signs you have a deliverability problem

• Open and click rates drop suddenly across all campaigns, especially for Gmail addresses.
• Your flows' revenue per recipient falls with no change to the flows. Revenue from your abandoned cart flow is usually the first to show it.
• Bounces rise. Check them with the bounce rate calculator, then see which ones Klaviyo suppresses for you in my guide to hard bounce vs soft bounce in Klaviyo.
• Postmaster Tools shows a rising spam rate or a falling domain reputation.

If you see two or more of these, pause sends to unengaged segments, check DNS again and send only to your most engaged people for a week or two while things recover.

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