Quick answer: Gmail and Yahoo expect anyone sending marketing email to authenticate their domain (SPF, DKIM and DMARC), offer an easy one-click unsubscribe, and keep spam complaints very low (Google recommends staying under 0.1%, and never reaching 0.3%). The strictest rules formally apply to "bulk senders" (around 5,000 messages a day to personal Gmail accounts), but following them is smart for every store, because inbox providers are getting tougher on everyone.
If you send marketing email from Shopify, Klaviyo, Mailchimp or similar, you might have seen warnings about "sender requirements." They sound technical, but the practical checklist is short. And with the holiday season close, now is the time to check it, because a rushed campaign from a poorly set-up domain is exactly when email gets throttled.
A note on sources: details vary between vendor blogs, and the exact thresholds and enforcement timing have been reported differently. Treat this as a practical summary and confirm specifics on Google's and Yahoo's official sender guideline pages.
The checklist
1. Authenticate your sending domain
Authentication proves that your emails really come from you. There are three parts:
- SPF lists which servers may send mail for your domain.
- DKIM adds a digital signature to your messages.
- DMARC tells receivers what to do if SPF or DKIM fail, and gives you reports. A basic policy (even "p=none" to start) is generally treated as the minimum, and many senders move to stricter policies over time.
In Klaviyo, Shopify Email and most platforms, you'll find a "domain authentication" or "sending domain" setup. It involves adding a few DNS records at your domain provider. If this is new to you, ask someone to do it, because a wrong DNS record can also break your regular email.
2. Use a branded sending address
Send from an address on your own domain (hello@yourstore.com), not a free Gmail or Yahoo address. Sending marketing email from a free-mail address fails modern authentication checks.
3. Make unsubscribing easy
Marketing emails should include a visible unsubscribe link, and the major platforms add a one-click unsubscribe header (the technical standard behind that "Unsubscribe" button at the top of Gmail). Honor opt-outs promptly. Hiding the unsubscribe link might reduce opt-outs in the short term, but it pushes people toward the "Report spam" button, which hurts you far more.
4. Keep spam complaints low
Google's guidance is to stay below roughly 0.1% spam-reported rate in Postmaster Tools, and to never let it reach 0.3%. Yahoo cites a similar line. In practice, that means:
- Only email people who signed up or bought.
- Don't buy or rent lists. Ever.
- Send what you promised. If someone signed up for a 10% discount, don't send them daily promotions.
- Remove people who haven't opened anything in many months. A smaller, engaged list beats a big dead one.
5. Watch your engagement
Inbox providers look at whether people open and click, reply, delete without reading or mark as spam. A flow that people appreciate (a welcome series, an order update) builds your reputation. A weekly blast nobody wants damages it.
6. Set up Google Postmaster Tools
It's free. After you verify your domain, you can see your domain reputation and spam rate as Gmail sees them. Check it monthly.
What goes wrong most often
- Different tools sending from the same domain, each with its own (or no) authentication. Your Shopify order emails, your Klaviyo campaigns and your helpdesk should all be authenticated.
- A sudden spike. Sending to your full list for the first time in months on Black Friday is a classic way to trigger throttling. Warm up gradually with your most engaged contacts first.
- Old, unengaged contacts. They inflate complaint rates and lower engagement.
- Broken links or misleading subject lines. They increase complaints.
A simple pre-holiday routine
- Verify SPF, DKIM and DMARC for your sending domain.
- Check Postmaster Tools for spam rate and reputation.
- Clean your list: suppress contacts with no engagement in 6 to 12 months (or run a short re-engagement series first).
- Start campaigns with your most engaged segment and widen over a few days.
- Test that unsubscribe links work.
Our Black Friday checklist puts this in the week-by-week plan.
Why this matters beyond deliverability
Email is one of the highest-return channels for small stores, and most of the money is in automated flows, not campaigns: welcome, abandoned cart, post-purchase and winback. If those emails land in spam, you lose revenue quietly. See our guides on abandoned cart emails and Shopify's automation ideas.
Need help?
We set up and test Klaviyo flows inside your account, including checking your sender authentication, branded templates and sign-up forms. See our email and SMS flows setup, or send us a short brief for a written quote.
Frequently asked questions
Do the Gmail and Yahoo rules apply to my small store?
The strictest rules apply to senders of around 5,000 or more messages a day to personal Gmail accounts, but authentication, easy unsubscribes and low complaint rates are good practice for every sender.
What are SPF, DKIM and DMARC?
SPF lists the servers allowed to send for your domain, DKIM signs your messages, and DMARC tells receivers what to do when checks fail and sends you reports.
What spam complaint rate is acceptable?
Google recommends keeping the spam rate in Postmaster Tools below 0.1 percent and never reaching 0.3 percent.
Can I send marketing email from a free Gmail address?
No. Send from an address on your own authenticated domain, such as hello@yourstore.com.
Related services
- Klaviyo Email & SMS Flows Setup for Shopify โ welcome, cart, post-purchase and winback flows
- Monthly Shopify Store Management & Support โ ongoing changes, fixes and check-ups each month
- Shopify Subscriptions & Recurring Billing Setup โ subscription plans, billing and a customer portal, tested end to end
