> ## Documentation Index
> Fetch the complete documentation index at: https://docs.apollodeploy.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Send emails with Kotlin

> Send a transactional email with the official Apollo Signal Kotlin SDK

The Kotlin JVM 21 SDK provides a coroutine-based class client and uses
`https://api.signal.apollodeploy.com` by default.

Before you start, [create an API key](/signal/create-an-api-key) with **Emails: Send** permission
and [verify the From domain](/signal/add-a-domain).

<Steps>
  <Step title="Install the SDK">
    ```kotlin theme={"dark"}
    dependencies {
        implementation("com.apollodeploy.signal:signal-sdk-kotlin:4.0.1")
    }
    ```
  </Step>

  <Step title="Store your API key">
    Set `SIGNAL_API_KEY` in the server environment or secret manager.
  </Step>

  <Step title="Send an email">
    ```kotlin theme={"dark"}
    import com.apollodeploy.signal.sdk.ApolloSignalApiClient
    import com.apollodeploy.signal.sdk.ClientConfig
    import com.apollodeploy.signal.sdk.models.SendEmailRequest

    suspend fun main() {
        val signal = ApolloSignalApiClient(
            ClientConfig(
                defaultHeaders = mapOf(
                    "Authorization" to "Bearer ${System.getenv("SIGNAL_API_KEY")}",
                ),
            ),
        )

        try {
            val email = signal.emails.sendEmail(
                SendEmailRequest(
                    from = "auth@mail.company.com",
                    to = listOf("alex@example.com"),
                    subject = "Reset your password",
                    text = "Use the secure link in your account to choose a new password.",
                ),
            )

            println(email.id)
        } finally {
            signal.close()
        }
    }
    ```
  </Step>
</Steps>

<Note>
  The SDK operations are suspending functions. Reuse one client for the lifetime of your service and
  close it during application shutdown.
</Note>

<CardGroup cols={2}>
  <Card title="Java" icon="code" href="/signal/send-with/send-with-java">
    Use the Java 17 SDK.
  </Card>

  <Card title="All SDKs" icon="code" href="/signal/send-with/sdk-overview">
    Compare every supported language and framework.
  </Card>
</CardGroup>