Configuration

Every provider subpath exports three Layer constructors with the same shape. Each provides the Email service, so you can change the constructor or the provider without changing the code that sends.

Reading options from the environmentCopy Anchor Link

layerConfig resolves a Config into options. Called with no argument, it reads the provider's standard environment variables, for example RESEND_API_KEY for Resend.

Example (Reading the Resend Key From the Environment)

import { ConfigProvider, Layer } from "effect";
import * as Resend from "@effect-kit/emails/resend";

const EmailLive = Resend.layerConfig().pipe(
        
const EmailLive: Layer<Email, ConfigError | ResendConfigurationError, never>
  Layer.provide(ConfigProvider.layer(ConfigProvider.fromEnv())),
);

The ConfigProvider layer is what reads process.env. Loading a .env file is up to your application.

Every provider's layerConfig has a default Config except Mailtrap, which needs an explicit one because it has no default.

Example (Passing an Explicit Config to Mailtrap)

import { Config, ConfigProvider, Layer } from "effect";
import * as Mailtrap from "@effect-kit/emails/mailtrap";

const EmailLive = Mailtrap.layerConfig(
  Config.all({
    token: Config.Redacted("MAILTRAP_TOKEN"),
    mode: Config.succeed("production" as const),
  }),
).pipe(Layer.provide(ConfigProvider.layer(ConfigProvider.fromEnv())));

Passing options directlyCopy Anchor Link

layer takes resolved options. Secrets are Redacted values, which stay hidden when the options are logged.

Example (Building the Resend Layer With Options)

import { Duration, Redacted } from "effect";
import * as Resend from "@effect-kit/emails/resend";

const EmailLive = Resend.layer({
  apiKey: Redacted.make("re_fake_key"),
  timeout: Duration.seconds(10),
});

A Redacted secret must be printable ASCII with no spaces. A value that is not fails Layer construction with a configuration error naming the field.

Using your own clientCopy Anchor Link

layerClient borrows a client you created and never closes it. The client keeps its own retry, timeout and logging policy.

Example (Borrowing a Resend Client)

import { Resend as ResendSdk } from "resend";
import * as Resend from "@effect-kit/emails/resend";

const client = new ResendSdk("re_fake_key");

const EmailLive = Resend.layerClient(client);

The same seam works in tests: pass any object that has the methods the Layer calls. For Resend that is emails.send.

OptionsCopy Anchor Link

Options differ per provider. Resend is the worked example.

timeout also exists on the other providers. Its default is 30 seconds, except Azure, which polls a long-running operation and defaults to 60 seconds. A value that is not finite and positive fails with a configuration error whose field is "timeout".

Configuration errorsCopy Anchor Link

Layer construction can fail with a Config.ConfigError when a variable is missing, or with a provider configuration error such as ResendConfigurationError, whose field names the bad option. Handle both where you build the Layer, at the edge of your program.