Bulk SMS: how to build a campaign that converts

Start with a clean base and current marketing consent. Sending to people without consent risks fines and – just as costly – losing sender reputation with carriers. Make sure the list itself is in order: numbers in E.164 format, no duplicates and no contacts you already know are dead – that is the condition for good deliverability. Cleaning the base before a large send lowers cost (you do not pay for messages that have nowhere to land) and protects the delivery rate carriers watch.

One message to your whole base wastes SMS potential. Split recipients by what you know about them: purchase history, location, funnel stage, last-active date. A new customer gets a different SMS than one who has not bought in 60 days. Segmentation raises CTR and – importantly – cuts opt-outs, because the content is relevant.

An SMS has 160 characters per segment (beyond that the message splits into more, costlier segments). Every word counts. A proven structure: a recognizable sender (Sender ID), one concrete benefit, one clear CTA, a short link. Build the body for each recipient on your side – name, code, amount, whatever data you hold in your own system – and pass the finished text to the API. "Anna, your -15% code expires today at 10pm" beats "Sale in our store" every time. Personalised messages go out one by one through POST /api/sms; identical copy for a group goes in a single POST /api/sms-multi request – more on the bulk SMS page.

Timing matters. Send during hours of real recipient activity – for B2C typically 10am–12pm and 5pm–8pm, for B2B during work hours. Avoid early morning and late evening (irritation = opt-outs). The moment is decided on your side: your system fires the send at the hour you picked, and one POST /api/sms-multi request takes up to 100 numbers, so a large base goes out as a series of such requests, one after another.

Before sending to the whole base, test two copy versions on small samples and send the winner to the rest. Test one element at a time: CTA, length, presence of a discount, the hour. Even a few percentage points of CTR on a large base is real money. You run such a test on your side: split the base into two samples, send both versions through the API and compare the results in your own analytics.

Measure three things: deliverability (did it arrive), CTR (was the link clicked) and conversion (did the goal happen). Delivery comes from us: a webhook sends your address a DELIVERED or ERROR status for every message. Clicks and conversions you count on your side – a separate landing page URL or your own campaign tags tie a click to a purchase in your analytics. Calculate the cost in advance in the calculator: no subscription, the rate drops with volume. A test account with 100 free SMS is on the sign-up page.