SMS Marketing: How It Works and When It Pays Off
Basics4 minInnovialabs editorial team
In short
SMS marketing pays off when messages are short, timely and sent to people who opted in; measure target actions from SMS links and promo codes, not delivery.
The short answer
SMS marketing means sending messages to customers through an SMS gateway: reminders, order statuses, promotions, verification codes. Its strengths: SMS needs no internet or app, and the notification is seen right away. Its weaknesses: every message costs money, text length is limited, and unnecessary sends quickly annoy people.
SMS pays off where the message is useful to the recipient right now: delivery status, appointment reminder, abandoned cart, a personal offer for a regular customer.
How it works technically
- SMS gateway (aggregator) — a service that accepts your messages via API or a dashboard and passes them to mobile operators.
- Sender name (alphanumeric sender ID) — text shown instead of a number in the "From" field, such as your company name. It usually has to be registered with the aggregator or operators, and documents are often requested. Without a registered name, messages may fail or go out under a generic sender.
- Delivery reports — the gateway returns statuses: delivered, undelivered, expired. Store them to clean your database.
- Integration — SMS is usually sent by a CRM, website or bot on an event: order placed, payment received, visit tomorrow.
Transactional vs promotional messages
| Transactional (service) | Promotional | |
|---|---|---|
| Trigger | A customer action: order, payment, login | A business decision: sale, new product |
| Expectation | The customer expects it | The customer does not |
| Consent | Tied to the service | Requires separate explicit consent |
| Operator rules | Usually softer | Stricter: send times, templates, moderation |
Do not disguise ads as service messages: operators and aggregators check for this, and consequences range from a blocked template to a disabled sender name.
Consent and opt-out
- Collect explicit consent for marketing: a separate unticked checkbox in the form, not a default. Store the date and source of consent.
- Offer an easy way to opt out — a reply, a link or a short number — and honor it quickly.
- Do not send at night and do not overdo frequency.
- Rules for marketing messages and personal data vary by country. Before launch, check local law and your aggregator's policies.
Length and cost logic
You pay per segment, not per message. How many characters fit into a segment depends on encoding:
| Encoding | Single SMS | Per segment in a long SMS |
|---|---|---|
| GSM-7 (Latin without special characters) | 160 characters | 153 |
| UCS-2 (Cyrillic, emoji, special characters) | 70 characters | 67 |
Practical takeaways:
- A 100-character Cyrillic text is already two segments, so double the price.
- One "non-standard" character switches the whole message to UCS-2. For example, Uzbek letters with ‘ (o‘, g‘) — that character is not in GSM-7.
- Segment price depends on the aggregator, operator, country and volume — compare rates for your specific destinations.
- Trim text, use short links, cut filler words.
How to measure results
Delivery is not a result. Count actions:
- Add UTM tags to links (
utm_source=sms,utm_campaign=...) to see visits and conversions in analytics. - Use unique promo codes for the SMS campaign so offline purchases are visible too.
- Compare against a control group: part of the audience gets no SMS, and the difference in purchases shows the real effect.
- Do the math: the cost of sending the whole campaign versus the extra revenue.
- Watch opt-outs and complaints — a rise means frequency or content is not working for people.