What happens when the primary provider has a bad hour

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.

4 min read · updated 2026-10-12

Priority decides who goes first

Connections on a route carry a priority. The highest-priority connection that is healthy and still inside its pacing budget takes the message. Only when it cannot do so does the next one in line get it.

This is the arrangement that makes a second provider worth configuring. A single connection with no fallback has exactly one failure mode, and it is total.

Weight spreads load within a connection

Several sender numbers can be bound to one connection, each with a weight. Messages are distributed across them by that weight, so a number carrying a heavier share takes proportionally more traffic.

Because provider limits are typically per number, spreading across numbers within a connection is often the simplest way to raise real throughput without changing providers.

Failure is detected, not assumed

A connection that keeps rejecting sends is taken out of rotation rather than being retried indefinitely. Without that, one misconfigured connection at the top of a route becomes a single point of failure for every message behind it — the position where a mistake costs the most.

What failover does not promise

  • It does not guarantee delivery. It changes which provider carries a message, not whether the destination carrier accepts it.
  • It does not repair a bad route. If every connection on the route has the same misconfiguration, failover has nowhere to go.
  • It does not cover email or WhatsApp. Automatic failover is implemented for the SMS channel.

Keep reading

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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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