Short Message Service (SMS) is the standard text messaging service built into mobile networks. It carries short plain-text messages, up to 160 GSM-7 characters in a single segment, to and from virtually any mobile phone without an app or a data connection. For businesses, SMS is one of the most direct ways to reach customers and staff, used for alerts, reminders, appointment confirmations, two-way service conversations and, more cautiously now, login codes. Business texting at volume is shaped by carrier registration rules and consent laws as much as by the technology.
At a glance
- SMS carries plain text in short messages; longer messages are split into segments, and business plans typically bill per segment.
- It works on almost any mobile phone through the cellular network, with no app or mobile data needed.
- Businesses send SMS from software through providers, from regular phone numbers, toll-free numbers or short codes, each with its own registration rules.
- Consent and opt-out obligations apply to business texting and depend on message type and where recipients are.
- SMS login codes are convenient but weaker than app-based or phishing-resistant methods.
What problem it solves
Businesses need a fast way to reach people who may not open email or install an app. Nearly everyone with a mobile phone can receive a text, and texts are usually seen quickly. That makes SMS well suited to time-sensitive messages: delivery and appointment reminders, outage and fraud alerts, staff scheduling, and two-way conversations where a customer would rather text than call.
For a buyer, SMS also brings practical problems. Messages sent from software are treated differently by carriers from person-to-person texts, unregistered business traffic is increasingly filtered or blocked, and texting customers from employees’ personal phones leaves no business record. A proper business texting setup addresses all three.
How it works
Sending and delivery. A message goes from the sender’s phone or software to a message center run by the carrier, known as an SMSC. The SMSC stores the message and forwards it to the recipient’s carrier and phone, holding it and retrying for a period if the phone is off or out of coverage. Delivery is usually quick but not guaranteed, and delivery receipts vary in what they confirm.
Message size and encoding. A single segment holds 160 characters in the GSM 7-bit character set, or 70 UCS-2 units when the message needs characters outside that set, such as emoji or many non-Latin scripts. Longer texts are sent as linked segments, typically 153 or 67 units each, and reassembled on the phone. Emoji and GSM extension characters can each take two units, so actual segment counts vary; your provider’s encoding and segment preview shows what a message will cost.
Business sending. Businesses usually send through a communications platform as a service (CPaaS) provider, a contact center or a business phone service, which connects to carriers through aggregators. This kind of traffic is called application-to-person (A2P) messaging. In the US, sending from ordinary local numbers requires 10DLC registration of the business and its use case; toll-free numbers need verification; and short codes are leased and approved separately.
Replies and opt-outs. Recipients can reply to most business numbers. Carrier rules require handling standard keywords such as STOP and HELP, and senders need records of how consent was obtained.
When it matters for buyers
- When launching customer notifications or two-way texting. Number type, registration and consent records need to be sorted before sending, or messages may be filtered.
- When choosing between SMS, MMS and RCS. Multimedia Messaging Service (MMS) adds images and video; Rich Communication Services (RCS) adds branding and buttons where supported, usually with SMS as the fallback.
- When setting login security. If SMS codes are your main second factor, consider stronger options, at least for administrators. See two-factor authentication.
- When marketing by text. Rules are stricter for marketing than for transactional messages. In the US, the TCPA, state laws and carrier rules can all apply; which ones depends on the content, how numbers were collected and how messages are sent. Involve counsel.
- When warning staff about scams. Fraudulent texts, or smishing, are a common way attackers target employees and customers.
Questions to ask vendors
- Which number types can we send from, and do you handle 10DLC, toll-free verification or short code applications?
- How are messages priced: per segment, per message or bundled, and are carrier fees passed through?
- What throughput limits apply to our number type and registration?
- What delivery reporting do we get, and what does a “delivered” status actually confirm?
- How are opt-outs, HELP replies and consent records handled and stored?
- Can texts sync to our CRM, help desk or contact center so conversations are on record?
- Do you support MMS and RCS, and how does fallback work?
How it differs from MMS
SMS and MMS both arrive in the phone’s normal messaging app, but they are different services. SMS carries short plain text and reaches almost any phone. MMS carries images, audio, video and longer text, is usually downloaded over mobile data, and usually costs more per message for businesses. Many business texts start as SMS and switch to MMS only when media or longer content is needed. RCS is a third option that adds richer features where the recipient’s phone and carrier support it. For platforms that send and receive business texts at scale, see our communications platform as a service page.