SMS Marketing Agency for E-commerce

SMS is not an acquisition channel. It is the channel that catches what email no longer catches: expiring carts, short-window launches, segments that have stopped opening their inbox. Run as a second promotional channel, it burns a list in three months. Run as an urgency channel, it adds 8 to 15% of owned revenue without touching email deliverability.

We build SMS programs that survive past quarter one: compliant opt-in, strict segmentation, capped frequency, and measurement on revenue per send rather than click rate.

Why most SMS programs collapse within six months

The pattern is almost always the same. A brand switches SMS on ahead of Black Friday. The first sends go out to a fresh, still-engaged list and the numbers look spectacular: read rates above 90%, revenue per send three times email. The conclusion is mechanical : send more.

Six months later the list has melted. Every send costs money, unlike email, and revenue per send has quartered. The program gets shut down with the verdict that "SMS doesn't work for us".

What happened has nothing to do with the channel. An SMS list does not rebuild like an email list: acquiring a number costs more, consent is harder to obtain, and in the customer's mind opting out is final. An SMS program is managed like a depletable stock, not like a tap.

That is why we cap frequency in month one, before the question comes up.

What we handle

Opt-in collection

SMS programs die at the list level. A number collected without explicit consent is a number that exposes you and does not convert. We implement layered collection (email pop-up then SMS, or a combined form), double opt-in where the context requires it, and the disclosure language that must accompany every collection point.

For brands sending into France and the EU, our compliance framework follows CNIL guidance on SMS prospecting : prior, free and specific consent, stated purpose, and a simple opt-out in every message. See SMS and GDPR in France.

SMS flow architecture

Not every email flow deserves an SMS counterpart. We activate four, in this order:

1. Cart abandonment SMS, relaying the email flow, triggered at H+4 on carts above average order value.
2. Checkout abandonment, the most profitable window in the program.
3. Back in stock, where SMS consistently outperforms email.
4. Enriched transactional post-purchase on shipping, which opens the channel without spending promotional credit and cuts support tickets. See the Klaviyo post-purchase flow.

Welcome SMS and win-back come later, once the list is large enough for segmentation to mean anything. On dormant segments, the choice between an SMS win-back and a sunset flow is made on cost per reactivated contact, not on reply rate.

Campaign calendar

One rule: SMS never duplicates the day's email. It fires when time matters : final hours of a promotion, limited restock, expiring code. We cap frequency at 2 to 4 sends per month depending on vertical, and systematically exclude anyone who purchased in the last 7 days.

Segmentation

An SMS program without segmentation is a broadcast list. We build three axes minimum: recent engagement, customer value, and purchase behaviour.

The value axis rests on RFM segmentation, whose method is set out in RFM customer segmentation. VIP segments justify higher frequency and early access : see Klaviyo VIP segmentation. Low-engagement segments receive only major events, two or three times a year.

Email / SMS arbitration

The question is never "should we do SMS" but "which message earns an SMS". We provide a decision grid by message type and holdout-based incrementality measurement, to separate the revenue SMS creates from the revenue email would have captured anyway.

Platforms

We work primarily in Klaviyo SMS, whose decisive advantage is a shared customer profile with email: same segmentation, same suppression, same attribution. That is what makes a real non-overlap rule between channels enforceable.

We also work in Brevo where the list already lives there, and we can make a third-party SMS tool coexist with Klaviyo when an existing contract requires it : at the cost of a suppression sync that needs monitoring.

Implementation detail: Klaviyo SMS setup and opt-in flows and transactional vs marketing SMS.

How we measure

Three metrics, not thirty:

• Revenue per send, the only metric that correctly arbitrates volume against fatigue.
• 90-day cumulative opt-out rate, the fatigue signal that precedes collapse.
• Holdout-measured incrementality on high-volume campaigns.

These sit inside the wider framework set out in lifecycle email marketing KPIs.

SMS click rate is a readership indicator, not a performance one. We track it; we do not steer by it.

What we do not do

We do not rent lists. We do not send to numbers collected outside your own touchpoints. We decline cadences above one send per week on a general-audience list, because they destroy the asset the program exists to build.

The first 90 days

We work in three stages, each gated on the previous one holding.

Days 1 to 15 : audit and compliance. List health, consent evidence, existing collection points, and the overlap between what email already sends and what SMS is meant to add. This is where we find the two problems that appear in nearly every account we open: numbers collected without a separate consent tick, and an SMS tool whose suppression list has drifted from the email one.

Days 16 to 45 : collection and transactional. New collection points go live, and the transactional layer is enriched before any promotional message goes out. Shipping notifications carry the highest read rate of anything you will ever send, cost the least, and build the sending history the promotional layer will rely on.

Days 46 to 90 : flows, then campaigns. Cart and checkout abandonment first, back in stock next, campaigns last. Campaigns come last on purpose: they are the easiest part to run and the easiest to overdo, and starting there is how brands burn a list before the flows that pay for the program are even live.

At day 90 you have a documented frequency cap, a working non-overlap rule with email, and a revenue-per-send baseline to measure everything afterwards against.

Working with your existing setup

Most brands that come to us are not starting from zero. They have an SMS tool bought during a Black Friday, a list of uncertain provenance, and flows built by whoever had time.

We do not require a migration. Where the existing tool is contractually locked in, we keep it and build the suppression sync that makes it safe to run alongside Klaviyo. Where the list provenance cannot be documented, we rebuild consent through a re-permission campaign rather than pretending the problem does not exist : it costs volume once, and removes a liability permanently.

For brands running email on Brevo, we work in place. For brands on Klaviyo, consolidating SMS there is usually the single highest-return change available, because it turns two separate reporting surfaces into one customer profile. See Klaviyo omnichannel marketing.

FAQ

How much does an SMS marketing program cost?

Cost splits in two: routing, billed per message sent, and management. Routing rates vary by destination country and volume, which makes the segment you send to the main cost lever.

Is SMS marketing legal in the EU?

Yes, subject to prior, free, specific and informed consent for prospecting to individuals, collected separately from terms acceptance, with a simple opt-out in every message. Transactional SMS falls outside this regime.

Should we add SMS if we already run email?

Only if you have identified messages email does not deliver in time. Adding SMS as a second promotional channel on the same messages produces cannibalised revenue. A holdout test settles it within one campaign.

What SMS sending frequency should we not exceed?

Two to four sends per month on a general-audience list. High purchase-frequency categories tolerate the top of the range; durable goods stay at the bottom.

Can we import an existing phone list?

Only with consent evidence for every number, including date and collection point. Without it, the import exposes the brand and degrades program metrics immediately.

Getting started

Entry is an audit: list health, collection compliance, email/SMS overlap, and quantified potential per flow. The deliverable is a 90-day activation plan with flows ranked by profitability.

Request an SMS audit : or see our Klaviyo audit if your email program needs the same look.

Talk to Deliver about your programme