Split by job. Email carries depth: newsletters, storytelling, education and rich product content that a shopper reads at their own pace. SMS carries urgency: short, time-sensitive nudges that need to be seen in minutes. Most stores need both, assigned to different moments, not one competing with the other. And one rule above the rest: you have to respect SMS the way you respect email. It is a program, not a blast list.
The email versus SMS question is rarely either or. They are different channels with different strengths, and the stores that get the most from both stop treating them as substitutes. Email is a room with space to explain, show and persuade. SMS is a tap on the shoulder. The most common failure we find in audits is not the wrong channel choice; it is a list with no program, subscribers piling up while near-zero revenue comes back because nobody built the journeys, or a program with no list. Decide which channel owns which job, build both properly, and each earns its place.
Email gives you room. It is the right channel for depth, storytelling, and anything a shopper wants to consider rather than react to instantly. Use it for:
Email also carries more design and more words without feeling intrusive, and shoppers expect it to. Because inbox space is comparatively cheap in attention terms, email is where your program does its heavy lifting on narrative and detail. For ecommerce, that program almost always lives in Klaviyo, where flows, segments and campaigns share one profile of the shopper. Our guide to the seven core Klaviyo flows covers how that automation is built.
SMS is immediate and short. It lands on the lock screen and tends to be read quickly, which makes it powerful and easy to overuse. Reserve it for messages that genuinely benefit from speed and brevity:
Do not mistake scarcity for smallness, though. SMS is not email’s little brother. On accounts where journeys are personalised against high-intent segments, recent browsers of a category or repeat buyers due for a reorder, we have watched SMS out-earn email campaigns outright. The discipline is in the sending rules: unengaged subscribers get at most one SMS a week, with the rest of the volume reserved for engaged tiers. Used with that restraint, SMS stays a channel shoppers welcome rather than mute.
The two channels carry different expectations and different rules, and this is where email and SMS diverge most sharply. Email requires clear permission to send and an easy way to unsubscribe in every message. Keeping your list clean and honouring opt-outs promptly is both a legal expectation and a deliverability one.
SMS is held to a stricter standard because it reaches a personal device. As a general principle, SMS needs its own explicit opt-in. You should not assume that an email subscriber has agreed to receive texts. Collect SMS consent separately and clearly, make the terms plain at signup, and always provide a simple way to stop messages. Rules vary by region and change over time, so treat this as orientation rather than legal advice, and confirm current requirements for your markets with a qualified source. The practical takeaway: build separate, clearly labelled consent for each channel, and respect opt-outs on both immediately. A shopper who trusts how you handle permission is a shopper who stays subscribed.
The strongest programs do not run email and SMS as parallel lists. They combine both inside a single flow, on a shared suppression layer, and let each channel play to its strength at each step.
Take abandoned checkout as an example. The flow opens with an email that has room to show the product, answer objections and reassure on shipping or returns. If the shopper still has not converted a short while later, a brief SMS adds the nudge a text delivers better than an inbox message. Same flow, same intent, two channels each doing what it does best. A welcome flow can lead with email depth and use SMS for a single well-timed prompt. A back-in-stock alert often works best as SMS, with an email follow-up carrying the fuller story.
Three principles keep the two channels cooperating rather than colliding. First, assign a job to each channel per step, so the same message is not duplicated across both. Second, coordinate timing and suppression so a shopper who acts on one channel stops hearing about it on the other, immediately and automatically. Third, keep SMS scarce, because it interrupts, so use it only where speed and brevity clearly win.
One note on platforms. Email belongs in Klaviyo, but on the SMS side we have consistently seen dedicated platforms like Attentive and Postscript outperform Klaviyo’s native SMS in tooling, list growth and revenue per subscriber. That said, the program matters more than the platform, and a migration is a conclusion your data should reach, never a premise. Done well, email builds the relationship and carries the detail, SMS closes short, urgent gaps, and together they cover more of the journey than either could alone. If you want a combined approach mapped to your flows and buying cycle, our email team builds exactly this.
Neither is better in the abstract. Email is better for depth, storytelling and rich content shoppers read at their own pace. SMS is better for urgency and short triggers, and on accounts with personalised, high-intent journeys it can out-earn email campaigns. The strongest results come from running both as one coordinated program.
No. As a general rule, SMS requires its own explicit consent, separate from email. Do not assume email subscribers have agreed to texts. Collect SMS opt-in clearly and separately, and confirm current requirements for your regions with a qualified source before you send.
Less often than email, and tiered by engagement. Unengaged subscribers should get at most one SMS a week, with the bulk of your volume going to engaged tiers around genuinely time-sensitive or high-intent moments. Keep the channel scarce so subscribers keep it switched on rather than opting out.
Both can work well inside one flow. Lead with an email that has room to show the product and answer objections, then add a short SMS reminder later if the shopper still has not converted. Suppress across channels so a shopper who acts on one immediately stops hearing about it on the other.
Short and urgent ones: sale-ending reminders, low-stock and back-in-stock alerts, early-access windows, and shipping or delivery updates. If a message needs multiple images or a longer explanation, it belongs in email instead.
We assign each channel its job, coordinate suppression, and keep SMS scarce so shoppers stay subscribed.