Educational
Your first SMS through the API, in ten minutes
From generating an API key to a delivered message: the minimum steps for a working integration, with code samples and the mistakes people make on day one.
Knowledge base
Learn more about everything you can do with Calisero
Educational
OTP and 2FA: what they are, when to use them, how to get them right
One-time codes are the simplest barrier between a customer's account and whoever learned their password. Here is how to build them so they actually help.
Educational
Transactional or promotional SMS? The difference regulators see
The same infrastructure, two entirely different legal regimes. Classifying a message wrong brings complaints, route blocks and fines.
Educational
Webhooks: how you learn the message actually arrived
The API confirms you sent. The delivery callback tells you what happened next. Here is how to build one so you never lose an event.
More articles
Educational
Opt-out and GDPR: what you must do with an unsubscribe request
The right to stop receiving messages has no cooling-off period and no commercial exceptions. How to implement it technically without blocking necessary messages too.
Educational
Sender ID: choosing your sender name, and why it matters more than you think
The displayed name is the first thing a recipient sees and the main reason they open or ignore the message. The Romanian rules and the practices that work.
Educational
Failed delivery: reading the status and knowing what to do next
An undelivered message always has a reason. A guide to interpreting statuses and the right action for each — including when retrying is the mistake.