Amazon SNS sends SMS one-time codes for this environment. A newly connected SMS provider becomes the one that sends. Other connected SMS providers stay as fallbacks after a hard failure. With none connected, SMS sign-in and SMS MFA cannot send a code. Authenticator-app MFA does not need SNS.

## Prepare SNS

In AWS, confirm the account can publish SMS in the region you will use, and that the account is out of the SMS sandbox if you need to reach arbitrary numbers. Create an IAM key that can publish SMS. Do not reuse a general administrator key.

Spend limits and origination identities are enforced by AWS. A successful save in Authdog does not raise the SNS spend limit.

## Connect Amazon SNS

In the [Authdog console](https://console.authdog.com):

1. Select the project and environment.
2. Open **Notifications > Providers**.
3. Select the **SMS** channel.
4. Choose **Amazon SNS** and select **Connect**.
5. Enter:

| Field | Value |
| --- | --- |
| **Access key ID** | The IAM access key |
| **Secret access key** | Stored encrypted. Leave blank on a later edit to keep the stored secret |
| **Region** | The SNS region, for example `us-east-1` |
| **Sender ID** | Optional. An alphanumeric sender the region allows, for example `Authdog` |

6. Save. Amazon SNS becomes the active SMS provider.
7. Select **Test** and confirm the message arrives.

Some countries reject a sender ID or require a registered origination number. If the test is accepted by Authdog and never arrives, check the SNS delivery log for that region.

## Use it for sign-in or MFA

SMS codes are a channel. Turn the method on separately.

1. For passwordless sign-in, open **Authentication > Methods** and enable **SMS**.
2. For a second factor, open **Authentication** and enable **Multi-factor authentication**, then enroll a test user with SMS before you enforce it.
3. Sign in and confirm the code arrives.

Use a separate key and region for production. Providers do not copy between environments.

## Related

| Read | To learn how to |
| --- | --- |
| [SMS code](/marketplace/sms-otp/setup) | Enable the passwordless SMS method |
| [Multi-factor authentication](/docs/mfa) | Enrollment, reset, and which factors count |
| [Marketplace](/marketplace/amazon-sns) | The listing for this integration |