There is no channel that gets read like SMS. Open rates sit near universal, and most messages are looked at within a few minutes of arriving. Email would sell its soul for those numbers.
Which is exactly what makes it dangerous. A mediocre email gets ignored and costs you nothing. A mediocre text interrupts someone’s evening on the device they keep in their pocket, and the punishment is immediate — they unsubscribe, or they mark you as spam, or they simply think slightly less of you. There’s no middle ground where a bad SMS quietly does no harm.
So the whole discipline of SMS marketing is restraint. Fewer messages, better reasons, ruthless relevance. Get that right and it outperforms almost everything. Get it wrong and you burn a list you spent months building.
Consent is the entire foundation
Start here, because everything else is built on it. You need explicit, provable permission to text someone — not an email address you happen to have, not a phone number collected for delivery purposes, not a business card from an event.
Rules vary by country and they’re getting stricter, not looser. The consistent principles across most of them: the person must actively opt in, they must know what they’re signing up for and roughly how often, and they must be able to stop instantly. Keep a record of when and how each person consented. If a complaint ever lands, that record is the entire defence.
The temptation to upload a list of customer phone numbers you already have is strong and the answer is no. Numbers collected to deliver an order were not given to you for marketing, and using them that way is both a legal problem and a fast route to complaints.
Email forgives a list you built carelessly. SMS does not — it just turns your best channel into a stream of complaints.
How to actually build the list
Ask at moments when a text is obviously useful to them rather than to you. At checkout, for delivery updates. At booking, for appointment reminders. On a form, with a clearly separate tick box that isn’t pre-ticked and isn’t bundled with the email consent.
Be specific about what they’ll get. “Get order updates and occasional offers, around two texts a month” sets an expectation you can keep. “Sign up for news” sets no expectation at all, which means every message you send has a chance of feeling like too many.
- A separate, unticked box at checkout or on a form — never bundled with email
- A keyword people can text to join, useful on packaging, receipts and signage
- A QR code at a physical location or on print, pointing at a short signup
- In an email to subscribers who already engage, framed as a faster way to hear about specific things
- After a booking, offered as reminders rather than marketing
What’s actually worth sending
The test for every SMS is simple: would this person be mildly pleased to see it, or mildly annoyed? Anything that fails is an email.
Transactional and time-sensitive messages pass easily. Order shipped, appointment tomorrow, table confirmed, delivery is fifteen minutes away. These are genuinely useful, and they also warm people up for the occasional promotional message because the channel has earned its place.
Promotional messages need a real reason to be urgent. A flash sale ending tonight works. A sale running all month does not — that’s an email, and sending it by text just spends goodwill you’ll want later.
The third category, and the most underrated, is the genuinely personal one. A stylist texting a regular that a cancellation opened up on Saturday. A garage saying the part arrived. These convert extraordinarily well because they’re not campaigns at all — they’re service.
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There is no subject line, no header image, no scrolling. The whole message lands at once and gets judged in about two seconds.
Say who you are immediately — people don’t have your number saved, and an anonymous text reads as spam before it reads as anything else. Then the point, then the action, then the exit. That’s the entire structure.
Keep links short and obviously yours. A bare shortened link from a generic service looks exactly like a phishing attempt, and plenty of people have learned not to tap those. A branded short domain is worth the small effort of setting up.
And include the opt-out every time. It’s usually a legal requirement, but beyond that it’s reassurance — a visible way out makes people less twitchy about staying in.
Frequency is the thing that kills lists
Most SMS programmes die from volume rather than content. The messages were fine; there were just too many of them.
Two to four promotional messages a month is a reasonable ceiling for most businesses, and plenty do well with fewer. Transactional messages sit outside that count because people want them. If you’re unsure, send less — the cost of under-messaging is some missed revenue, and the cost of over-messaging is the list itself.
Watch your opt-out rate per send rather than in aggregate. A sudden spike after one message tells you precisely which message went wrong, which is far more useful than a monthly average that smooths it away.
Timing matters more here than anywhere
An email at 11pm waits politely in an inbox. A text at 11pm lights up a phone on someone’s bedside table. Many jurisdictions set legal quiet hours, and where they don’t, common sense should.
Mid-morning and early evening tend to work. Avoid very early, very late, and the middle of a working meeting-heavy afternoon. And respect time zones properly — if your list spans regions, send by local time rather than yours. Getting this wrong once produces a wave of opt-outs you can’t undo.
Segment, because relevance is the whole game
Blasting an entire list is what makes SMS feel like spam. The same message is delightful to one group and irritating to another, and the irritated group leaves.
Segment on things you actually know: what they bought, where they are, how recently they engaged, whether they’re a first-time or repeat customer. A message about a new arrival in a category someone already buys from is welcome. The same message to someone who bought once, two years ago, in a different category, is noise.
This is where SMS and your customer records need to talk to each other. If your CRM knows purchase history and your SMS tool doesn’t, every send is a guess. And if you’re running SMS alongside WhatsApp, our WhatsApp marketing guide covers how the two differ in tone and expectation.
Measure the right things
Open rate is almost meaningless here — nearly everything gets opened, so it tells you nothing about whether the message worked.
- Click-through rate on the link, which is the real engagement signal
- Conversion rate from click to the action you wanted
- Opt-out rate per campaign, watched for spikes rather than averages
- Revenue per message sent, which keeps frequency honest
- Delivery failures, which quietly indicate list decay
Revenue per message sent is the one that governs everything else. It forces the frequency question into the open: if adding a fourth monthly message lowers revenue per message and raises opt-outs, you’ve found your ceiling. Tag your links with UTM parameters so those clicks don’t land in your analytics as anonymous direct traffic.
Where SMS sits next to email
They’re not competitors, and using them the same way wastes both. Email is for depth — the newsletter, the long explanation, the browsable catalogue. SMS is for immediacy — the thing that matters in the next few hours.
A pattern that works well: email does the storytelling and the regular relationship, SMS handles the time-critical moment. Announce a sale by email, then text on the final afternoon. Confirm a booking by email, then remind by text the day before.
Used that way they reinforce each other rather than competing for the same attention. Our comparison of email marketing and social media makes a similar case about channel roles — the principle is the same.
A short list of things not to do
Don’t buy phone number lists. Don’t text people who gave you a number for a different purpose. Don’t send from a number that can’t receive replies — people do reply, and silence is a bad look. Don’t hide the opt-out. Don’t send four messages in a week because a campaign is going well. And don’t use urgency language when nothing is actually urgent; the channel is too intimate for that to survive repetition.
SMS rewards restraint more than any other channel. The businesses that do well with it send less than they could, about things people genuinely want to know, at times that don’t intrude. That’s not a limitation — it’s the reason the open rates stay as high as they do.