SMS fallback
When a contact can't receive RCS, Instasent delivers your message as an SMS instead — automatically. How it triggers, how it's set up, and how it's billed.
RCS is the rich, interactive version of your message. SMS fallback is the automatic plan B: when a contact can't receive the RCS, Instasent delivers the message to them by SMS, so the send isn't lost. You don't do anything on each send — just leave fallback enabled.
In short: RCS is tried first; if it can't get through, it goes out as SMS; and no one is left without your message.
When fallback happens
A message falls back to SMS when RCS can't deliver it. It happens in three cases: the contact's device or app doesn't support RCS, the operator returns an error, or the RCS message isn't delivered. In any of them, that contact's message is sent as an SMS and the original is marked Fallback.
The decision is made automatically, one contact at a time: if the contact can receive RCS, it's delivered over RCS; if not, it's delivered over SMS.
flowchart TD
S{"Can the contact receive RCS?"}
S -->|Yes| RCS["Delivered over RCS"]
S -->|No| SMS["Delivered over SMS (Fallback)"]
The discarded RCS attempt isn't charged. If the SMS fallback runs, the billing conditions of the SMS sent apply.
Turning on fallback
The fallback sender is set in two places, and the second one wins for that send.
On the RCS sender, its detail sheet has an SMS fallback sender field — the SMS sender used when RCS can't deliver. Setting it here is what makes every campaign built on that RCS sender start out with the right fallback already chosen.
When you create the campaign you pick an RCS Sender and, next to it, the SMS fallback sender. It isn't optional: every RCS campaign carries a fallback, so the SMS sender is needed to create it at all. It comes pre-filled — with the sender paired on the RCS sender if there is one, otherwise with your project's default SMS sender — and you can change it right there or later, while the campaign is still a draft, from its Details.
If your project has no active SMS sender, you won't be able to create the campaign: add one first.
Automations work the same way: the fallback sender is picked when you create them, using the same form.
And you can turn it off for one send. Fallback is on by default: in the Message step, between the RCS message block and the SMS one, the "If RCS is undeliverable" connector has a switch you can turn off if you don't want an SMS fallback that time.
By default, the fallback SMS repeats the text of your RCS message, and you can customize it — keeping in mind the SMS length and encoding rules.
What gets billed
There are three cases, depending on how the send ends:
- It can't be sent as RCS. The discarded RCS attempt is not charged.
- The SMS fallback runs. The SMS sent is billed under the SMS channel's conditions, even if it ends with a "Failed" status (for example, an inactive number): what's charged is the SMS that was sent, not its outcome.
- It can't be sent on any channel — no RCS, no SMS (for example, a country without coverage or without an authorized sender). A send that never went out isn't charged.
In your analytics
RCS and its SMS fallback are reported separately so you can see how each performed. In the campaign results, the Channels breakdown lists an RCS row and a second SMS row tagged as fallback, each with its own counts. A message routed to SMS carries the Fallback status. The header metrics and aggregate campaign stats already include every channel in the chain.
To see how many of your contacts need fallback in the first place, check the RCS support breakdown in Availability & rollout.