About Sendbox
Sendbox is a mass messaging platform based in Almaty, Kazakhstan. Its users run SMS, voice robot, WhatsApp, Telegram and email campaigns from one account. Its voice robot handles up to 1 million calls a day, by Sendbox's own count.
A Feature Its Users Pay For
Sendbox users pay for the traffic they send, including messages to numbers that never deliver. Sendbox wanted a paid feature that cleans a list before the campaign runs. It chose to resell ScoreMachine checks under its own product name. That made validation a new line of revenue.
What Runs on Each Number
eHLR. Returns valid, invalid or unknown on each mobile number. It combines telecom network signals with digital footprint data.
MNP. Returns the network holding the number today, after porting.
Connectability score. phone_accessibility ranks each number from 0 to 10 by how reachable it is.
Sendbox resells every method. Those three carry most of its volume.
Sendbox users see the results inside Sendbox, as audience validation and contactability scoring.
Three weeks to go live. Most of that time went on the commercial side. The JSON-RPC contract was simple to build against, and the documentation was clear. The one catch was authentication: auth.login returns the token in the Token response header, not in the body.
Results
An average Sendbox campaign covered 3,634 numbers. Each was checked with eHLR before sending, then matched against its delivery result.
| eHLR verdict | Numbers | Delivered | Not delivered |
|---|---|---|---|
| valid | 2,395 | 2,041 | 354 |
| invalid | 750 | 271 | 479 |
| unknown | 489 | 36 | 453 |
| All | 3,634 | 2,348 | 1,286 |
Valid. Numbers eHLR marked valid delivered at 85.2%. The whole list delivered at 64.6%.
Unknown. 92.6% of unknown numbers did not deliver.
What skipping costs. Sending only to valid numbers skips 1,239 messages. 932 of them would not have delivered. The other 307 would have. Failed sends drop from 1,286 to 354, at the cost of that reach.
Sendbox now runs about 200,000 validations a month.
In Sendbox's Words
Validation became a paid feature for us, not a cost. We went live in three weeks, and most of that was commercial work. The API itself was simple. On a typical campaign, numbers marked valid delivered at 85%, against 65% for the list as a whole. That difference is what our users pay for.