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Email vs SMS marketing for ecommerce: which message goes where?

Email vs SMS marketing for ecommerce depends on the message and the consent you hold, not on which channel is in fashion. Our rule: if the message has detail, can wait a day and goes to a large list, send email. If it is short, urgent and the person agreed to texts, SMS can earn its place. Judge both on orders and margin, never on opens or clicks.

Growth economics & retention
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By Stan HeropolitanskiUpdated 3 November 2026

You rarely have to pick one channel. You pick which message goes through which door. The rest of this page is about making that choice on purpose.

Email and SMS, side by side

Aspect
Email
SMS
Best for
Longer content, product detail, newsletters, automated flows
Short, time-sensitive messages
Room for content
Plenty: images, links, several products
A line or two
Consent
Prior consent for advertising to consumers in France, per CNIL1
The same CNIL rule covers SMS1
Sending cost
Mostly fixed: the platform, not each message
Usually a cost per message
Main technical hurdle
Sender reputation and authentication
Consent records and opt-out handling
Unsubscribe
One-click unsubscribe required from larger senders by Gmail2
A simple, free way to object; rules vary by market
Risk if overused
Spam complaints, then the inbox stops delivering
Opt-outs and annoyed customers, at a cost per send
How to judge it
Orders and margin against a holdout group
Orders and margin against a holdout group

Neither column wins. The last row is the same on purpose.

What does each channel need before you send?

Email: consent and a sender reputation

Consent first. France's regulator CNIL says prior consent is needed before sending advertising by email, fax or SMS to consumers1. So, in France at least, email is not the "easy" channel in legal terms. It is only the cheaper one per message.

Then the technical side. Gmail's sender guidelines ask all senders to authenticate with SPF or DKIM and to keep the spam rate reported in Postmaster Tools below 0.3%2. Senders of more than 5,000 messages a day to personal Gmail accounts must also set up SPF, DKIM and DMARC, and support one-click unsubscribe for marketing and subscribed messages2. Yahoo asks bulk senders for SPF and DKIM, a DMARC policy of at least p=none, one-click unsubscribe and a spam rate below 0.3%3.

In plain terms: if mailbox providers stop trusting you, your best email never reaches the inbox.

SMS: consent and a budget per message

CNIL says consent must be free, specific, informed and unambiguous; pre-ticked boxes are not acceptable, and accepting the terms of sale is not consent1. Our view: record consent per channel, and treat a yes to email as separate from a yes to texts.

CNIL also describes an exception for existing customers and similar products, provided they can object simply and free of charge1. It adds that simply creating an account does not make someone a customer for that exception4. That is one regulator's view of French law. For your markets, your counsel decides.

Then the cost. A guide from a reviews-software vendor says SMS gets expensive fast and carries legal risk most guides gloss over5. Shopify's own SMS guide frames the legal side around US laws such as the TCPA6. Useful, but written for a different legal system.

When to choose which

Choose email when

  • The message needs more than two lines: a new range, a guide, a comparison.
  • It can wait for the customer to open it later.
  • It goes to a large share of your list.
  • You run automated flows: welcome, abandoned cart, post-purchase, win-back.

Choose SMS when

  • The message is short and loses value with time: back in stock, order ready, a sale ending today.
  • The customer explicitly agreed to texts.
  • The margin on the likely orders covers the cost of every message, including the ones that sell nothing.

Use both when

The same customer journey has a detailed step and an urgent step. Email carries the detail. SMS carries the nudge. Our view: set a rule for who gets which, so one customer does not get the same offer twice in an hour.

How do you tell which channel earns its keep?

Not by opens. Our view: opens and clicks show attention, not sales. Look at orders and margin.

Our convention is contribution margin before marketing: revenue minus product cost, delivery, payment fees, returns and discounts. Then compare a group that got the message with a holdout group that did not.

Example (illustrative). 10,000 customers get a back-in-stock text. A holdout of 1,000 gets nothing. The texted group places 300 orders; the holdout places 25, or 250 per 10,000. The text added about 50 orders, not 300. If those 50 orders do not cover the cost of 10,000 messages in contribution margin, the text lost money while looking busy.

Our view: messages to existing customers easily collect credit for orders that would have happened anyway. The holdout is how you find out.

Our take

Start with email. It is cheaper per message, carries more, and the setup (authentication, consent, flows) is work you need anyway. Add SMS where a message is short, urgent and worth more than it costs to send.

Do not add SMS because a platform demo made it look easy. Add it when you can name the message it will carry and the margin it has to beat.

For the wider plan, read our customer retention strategy for ecommerce. For consent and copy in more depth, see SMS marketing for ecommerce. If you are comparing tools, start with the category page on SMS marketing platforms for ecommerce. We do not rank vendors.

For ZFD: Retention is in our offer in full, from audit and strategy to tool set-up and email, SMS and lifecycle work. See our ecommerce retention agency page for scope.

When we are not the right fit

FAQ

A rider in a red cape and bicorne hat on a rearing yellow plush horse, after David's Napoleon Crossing the Alps

Is SMS better than email for ecommerce?

Neither is better in general. Email suits detailed, less urgent messages to large lists. SMS suits short, urgent messages to people who agreed to texts.

Do I need separate consent for SMS and email?

CNIL says consent for advertising by email or SMS to consumers must be prior, free, specific, informed and unambiguous1. Our view: record it per channel. Your counsel decides what applies in your markets.

Can one consent checkbox cover both channels?

That depends on your markets and wording, so your counsel decides. Our view: separate choices are clearer for the customer and easier to prove later.

What does an email sender need to set up?

Gmail asks all senders for SPF or DKIM and a low spam rate; larger senders also need DMARC and one-click unsubscribe2. Yahoo sets similar requirements for bulk senders3.

How do I measure whether SMS is worth it?

Hold back a group that does not get the message, then compare orders and contribution margin. Subtract the cost of every message sent, not only the ones that converted.

“Their engagement is impressive.”
Marta PodhoreckaMarketing Manager, Brandline Group · Clutch review

Sources

  1. Prospection commerciale par SMS : le consentement - CNILPrimary source
  2. Email sender guidelines - Gmail HelpPrimary source
  3. Sender Best Practices - YahooPrimary source
  4. La prospection commerciale par courrier électronique, SMS-MMS et automate d'appel - CNILPrimary source
  5. SMS marketing for ecommerce: a complete 2026 guide - Wiser ReviewVendor
  6. sms marketing for ecommerce - ShopifyVendor

Next step

Want to check which of your messages pay for themselves? Book a call about your retention setup.

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