What SMS marketing actually is
SMS marketing is the practice of sending promotional or lifecycle text messages to recipients who explicitly opted in to hear from you. It splits from transactional texting the same way email does: a shipping confirmation is transactional, a flash-sale alert is marketing. That line matters because the consent and compliance rules tighten the moment a message promotes something. See transactional vs marketing email for the same boundary applied to inboxes.
Express consent comes first
In the United States, marketing texts sent with automated technology are governed by the Telephone Consumer Protection Act (TCPA). The long-standing standard for promotional texts is prior express written consent: a clear, documented agreement — a checked box, a keyword reply, a signed form — that names your business and authorizes marketing texts to that specific number. Pre-checked boxes and consent buried in unrelated terms do not count. The legal landscape is in motion; a 2026 Fifth Circuit ruling questioned whether the statute itself mandates written consent, so treat documented express consent as the safe floor, not a settled ceiling. None of this is legal advice.
A2P 10DLC: register or get filtered
If you send application-to-person texts from a standard 10-digit US number, carriers require A2P 10DLC registration — you register your business (a Brand) and each use case (a Campaign). This is a carrier and provider framework, not a law, but the consequences are concrete. As of 2025, US carriers filter or block traffic from unregistered 10DLC numbers and add per-segment surcharges, while registered traffic gets lower filtering and higher throughput. Providers like Twilio document the whole flow. Budget a few days for approval before your first send, and expect volume and content to be tied to what you registered — a platform that runs SMS as one channel among many should surface this rather than hide it, as covered in multi-channel vs omnichannel.
STOP and quiet hours
Every recipient can leave at any time. Guidance from CTIA expects senders to honor STOP and recognize plain-language opt-outs — stop, end, unsubscribe, cancel, quit — then send one confirmation and stop messaging until the person opts back in. Build opt-out handling into the channel itself, not a person's memory; your suppression list is the system of record, and once a number opts out, every journey and campaign must respect it. The same guidance points senders to avoid quiet hours, generally 9 pm to 8 am in the recipient's time zone and earlier in some states. Because phones travel, many teams hold sends to a conservative daytime window. Keep messages short, identify your brand, and set frequency expectations at sign-up.
When SMS beats email
Texts are read fast and almost always, which makes SMS strong for time-sensitive, action-required moments: a one-time passcode, an abandoned-cart nudge with a short window, a sold-out restock, an appointment reminder. It is a poor fit for long-form storytelling, weekly digests, or anything that can wait. The honest tradeoff is cost and intrusion — every segment costs money and lands on a lock screen — so SMS works best as a sharp accent inside a broader plan, not the backbone. Tools that bundle email and SMS, like Klaviyo, make the second channel easy to over-use; the discipline is yours to keep.
SMS earns its keep as one node in a coordinated flow, not a standalone blast. A welcome series might confirm an order by email and send a delivery alert by text; a win-back might try email first and reserve a single SMS for the highest-value churned accounts. Map where a text genuinely outperforms the inbox in lifecycle marketing for startups, and remember the scope: the TCPA, A2P 10DLC, and CTIA guidance are US-specific, while consent standards and quiet-hour rules differ by country. On fromHello, SMS is one channel a growth platform orchestrates alongside email, push, and in-app, with consent and suppression shared across all of them. Treat this guide as a starting map, not legal advice.