Bring your own account
The platform has no provider account of its own. That one design decision changes who owns the numbers, who holds the quota, and who appears on the invoice.
Read the guide →Which rate limit you just hit
There are two throttles in front of a send: the one your plan sets, and a much higher one at the network edge. Both answer with the same status code, so the message text is what tells them apart.
Two layers, two purposes
The plan limit is a product limit: it varies by subscription tier and is the number you can reason about and budget against. The edge limit sits in front of everything and exists only to keep anomalous traffic away from the service — it is set far above any plan ceiling, so a well-behaved integration should never see it.
Telling them apart
Both return the same throttling status, and both carry the same business code. What differs is the message text: the edge limit identifies itself with a distinct prefix. Without that distinction you cannot tell "you are sending faster than your plan allows" from "something upstream flagged this traffic", and the two call for different responses.
Retrying is not the same as fixing
- Throttling is a pacing signal, not a failed message. Backing off and retrying is correct behaviour.
- Retrying faster never helps: the limit is enforced on a one-second fixed window, so a burst inside the same window simply fails again.
- Sending, bulk sending, scheduled sending and the API all draw on the same allowance — they are not separate buckets.
Keep reading
SMS segments and what you actually pay for
SMS is billed per segment, not per message. Whether your text fits in one segment depends on the character set it needs — and on the encoding you set on the connection.
Read the guide →Opt-out handling
Opt-out is two halves: the suppression record, and the check that runs before a marketing message is handed to the provider. Both run through one shared normalisation, which is the part that usually breaks.
Read the guide →Reading a delivery receipt
A receipt is a sequence of states, not a verdict. Treating an intermediate one as final is the most common way a sending dashboard ends up lying to you.
Read the guide →Pacing, quotas and why we queue
Every connection carries a send rate. The platform queues to that rate instead of firing as fast as a provider will accept, because the fastest way to get throttled is to send at the speed that causes it.
Read the guide →Routing and failover
Routes are ordered by priority and weighted within a connection. The point of the arrangement is that a provider rejecting sends degrades into slower sending, not into silence.
Read the guide →Who decides whether a message is marketing
The platform asks you to declare what kind of message you are sending instead of inferring it from the text. That one field decides whether the opt-out gate applies — and the honesty of the declaration is yours.
Read the guide →A timeout is not a failure
Sending is accepted asynchronously and there is no de-duplication key. Retrying a request you are unsure about sends a second message and bills for it.
Read the guide →Two endpoints that look alike and are not
Delivery receipts and inbound replies are different endpoints, configured in different places in your provider’s console. Configure only the receipt URL and opt-out handling stops — silently, with no error anywhere.
Read the guide →Getting a number back
A recipient who opted out can opt back in. The platform deactivates the suppression record rather than deleting it, so the consent trail survives.
Read the guide →What happens when your callback is down
Terminal outcomes are pushed to a URL you control, with a small bounded retry. Your handler has to tolerate a repeat, and it should not expect a call for every message.
Read the guide →Who the recipient actually sees
If you do not name a sender, the platform picks one from the connection that carries the message. Naming one explicitly takes priority everywhere.
Read the guide →What the platform does not keep
Message content is not archived. What is kept is metadata — and among that metadata two fields are load-bearing, because without them a bill could not be reconciled.
Read the guide →