Short answer
Use SMS for timely, expected messages and measure incremental contribution against email alone. Price actual segments and check each destination’s rules.
The answer in detail
SMS can earn its cost when the message is urgent, short, and expected: a requested restock alert, an eligible cart reminder, or the final hours of a relevant private sale. Its economics depend on destination-country rates, encoding, platform charges, and incremental response. Its marketing rules also vary by country.
The benchmark
An SMS is billed by segment, not simply by the message as displayed on a phone. The original October 2026 article quotes Twilio's France destination price of US$0.0798 per segment before possible carrier charges. That is a dated French route example, not a global rate, a euro quote, or the price your marketing platform necessarily charges. Use the live country-specific quote and all relevant fees.
Twilio's primary character-limit documentation checked for this review distinguishes 160 GSM-7 characters in one segment and seventy UCS-2 characters. Concatenated messages generally have less room per segment—153 and sixty-seven respectively—because of their joining information. Unsupported characters can change the encoding of the entire SMS. Curly punctuation and emojis matter even in English.
The French original illustrates this with a seventy-nine-character message containing “fête” and a curly apostrophe: it becomes UCS-2 and needs two segments. GSM-7 supports é, è, à, and ù but not all French accented characters. For another language, check the actual final message rather than assuming the same character cost.
Marketing rules differ by jurisdiction. The English UK ICO guidance explains UK electronic-mail marketing rules, including consent and qualifying exceptions. The supplied FCC reference concerns US text-message regulation, a separate framework. Neither establishes one worldwide permission rule or sending window. Validate the current requirements for the recipient’s country, sender type and message purpose before sending.
The rule
Use SMS when three conditions hold together: the information loses value quickly, it fits a concise message, and the recipient expects this channel. A requested alert for the right size meets that brief better than a generic monthly newsletter.
Then calculate:
minimum incremental revenue per recipient = (segments × all-in price per segment) ÷ contribution-margin rate
This simplified threshold excludes other incremental fixed costs, which should be added where relevant. In a fictional USD example, two segments at $0.08 cost $0.16. With 40% contribution, the message needs $0.40 additional revenue per recipient over the email that would otherwise be sent. This convenient fictional segment price is independent of Twilio's country-specific quote. Include recipients who buy nothing in the denominator. Use the order contribution guide.
The steps
- Collect channel-specific permission. As a practical policy, distinguish SMS marketing permission from email and from a phone supplied for delivery. Offer a clear reason to subscribe and validate the applicable legal requirements. Do not treat transactional delivery updates as blanket promotional permission.
- Count eligible profiles. Shopify exports an Accepts SMS Marketing field separate from the phone number. Confirm the audience is eligible and that opt-outs propagate to every sending tool.
- Start with triggered flows. Try requested restock alerts first, then permitted cart reminders. Restrict campaigns to relevant trading events, with a predetermined frequency cap and opt-out monitoring.
- Write and count the final text. Use a recognizable sender, one useful link, and the destination's supported unsubscribe mechanism. Count the brand, link, and opt-out text before sending. An illustrative English draft is: “MAISON X: Your size is back in stock. See current availability: example.com/restock. Reply STOP to opt out.” This fictional draft is not a promise that reply-STOP works with every sender type or country. Test it in your platform's segment calculator.
- Measure incrementality. Keep a group receiving email alone. Compare revenue and contribution per assigned recipient, deducting actual SMS charges. The incrementality guide explains the comparison logic.
The pitfall
A delivery phone number is not evidence that someone wants promotional texts. A successful email flow is also not a reason to add SMS everywhere.
In one French fashion-brand example, an abandoned-cart SMS remained in English—“You left a few items behind!”—for French recipients, thirty minutes after abandonment. Another brand had no SMS subscribers despite thousands of email subscribers. Build a solid email audience first, then review one or two SMS scenarios in the recipient's actual language.
What to tell your team
These figures are fictional:
“Restock SMS generated $1.90 more revenue per recipient than email alone at $0.09 message cost. After checking contribution and local eligibility, we will test cart reminders and cap campaigns at two monthly for the 4,200 eligible subscribers.”
