Email is still one of the most profitable marketing channels, because you own the audience and each send costs almost nothing. In 2026 the winners combine two things: personalization based on what customers actually do, and the technical setup that keeps their messages out of spam.
Key takeaways
- Gmail, Yahoo and Microsoft now require authentication (SPF, DKIM and DMARC) from bulk senders.
- Marketing emails need one-click unsubscribe, and spam complaint rates should stay below 0.3%.
- Automated flows usually earn more than one-off campaigns.
- Personalize on behavior, not just a first name.
The inbox rules every sender must follow
Since 2024, Google and Yahoo have required anyone sending around 5,000 or more messages a day to their users to meet stricter sender requirements, and Microsoft introduced similar rules for Outlook addresses in 2025. In practice, every business should now:
- Authenticate your domain with SPF and DKIM, and publish a DMARC record.
- Send from your own domain, not a free Gmail address or your email platform’s shared domain.
- Offer one-click unsubscribe and process it within two days.
- Keep spam complaints low, ideally under 0.1% and never above 0.3%.
- Only email people who opted in. Bought lists are the fastest way to the spam folder.
If your open rates have dropped for no obvious reason, check these first. Google Postmaster Tools shows your domain’s reputation and spam rate for free.
What personalization means now
Adding a first name to the subject line is not personalization. Useful personalization uses what you know about each person:
- What they bought, to suggest refills, accessories or the next step
- What they browsed, to remind them about products or services they viewed
- Where they are, to show local stores, events, weather-related offers or shipping times
- How engaged they are, to send more to fans and less to people who rarely open
- Where they are in the journey, so a new subscriber, a first-time buyer and a loyal customer get different messages
AI tools now make this practical for smaller teams. They help write variations, choose send times and predict who is likely to buy again. A person should still check every message for accuracy and brand voice.
The five flows to build first
- Welcome series: three to five emails that introduce your brand and give a reason to buy or book.
- Abandoned cart or abandoned inquiry: a reminder within an hour, then a follow-up the next day.
- Browse abandonment: a gentle nudge when someone views products or services but does not act.
- Post-purchase: thank-you, how-to, review request and cross-sell.
- Win-back: a targeted message for customers who have not bought or opened in a while.
Service businesses can use the same idea: an inquiry follow-up, an appointment reminder, a review request and a check-in at the right time to rebook.
Do not forget SMS
SMS gets read within minutes, which makes it ideal for order updates, appointment reminders and time-limited offers. It needs explicit consent and should be used sparingly.
Our email and SMS team sets up authentication, builds these flows and reports the revenue they bring in. See what a bigger list could be worth with the growth calculator.
Frequently asked questions
How often should I send marketing emails?
For most brands, one to two campaigns a week plus automated flows. Send more to engaged subscribers and less to people who rarely open.
Is email marketing still worth it with AI inbox summaries?
Yes. Clear subject lines and a strong first sentence matter more than ever, because inbox AI often summarizes or previews your message before anyone opens it.
Which email platform should I use?
Klaviyo suits most e-commerce brands. Service businesses often do well with the email tool built into their CRM, or with Mailchimp or ActiveCampaign.