# MailerSend

> For the complete documentation index, see [llms.txt](https://effectkit.dev/llms.txt).

Send email through MailerSend with the @effect-kit/emails/mailersend Layer.

Source: https://effectkit.dev/docs/emails/providers/mailersend

The `@effect-kit/emails/mailersend` subpath sends messages through [MailerSend](https://developers.mailersend.com) and provides the `Email` service.

## Installation [#installation]

```package-install
@effect-kit/emails effect mailersend@3.6.0
```

The SDK is a pinned optional peer. It is needed only when you import this subpath.

## Setup [#setup]

`MailerSend.layerConfig()` reads these variables:

| Variable             | Required | Value   |
| -------------------- | -------- | ------- |
| `MAILERSEND_API_KEY` | yes      | API key |

**Example** (Sending a Message With MailerSend)

```ts twoslash
import { ConfigProvider, Effect, Layer } from "effect";
import { Email } from "@effect-kit/emails";
import * as MailerSend from "@effect-kit/emails/mailersend";

const EmailLive = MailerSend.layerConfig().pipe(
  Layer.provide(ConfigProvider.layer(ConfigProvider.fromEnv())),
);

const program = Effect.gen(function* () {
  const email = yield* Email;
  return yield* email.send({
    from: "hello@example.com",
    to: "ada@example.com",
    subject: "Welcome",
    text: "Your account is ready.",
  });
});

Effect.runPromise(program.pipe(Effect.provide(EmailLive)));
```

Use a `from` address your MailerSend account is allowed to send from.

## Options [#options]

`MailerSend.layer` takes these options. `layerConfig` builds the same object from a `Config`.

<TypeTable
  type={{
    apiKey: {
      type: "Redacted<string>",
      description: "The API key. Must be printable ASCII with no spaces.",
      required: true,
    },
    timeout: {
      type: "Duration",
      description:
        "Time allowed for one send. Must be finite and positive. When it elapses the send fails with TimeoutError.",
      default: "30 seconds",
      required: false,
    },
  }}
/>

## Capabilities [#capabilities]

MailerSend reports this in `email.capabilities`:

| Text | HTML | Both | Sender name | Cc  | Bcc | Reply-to | Headers | Attachments | Inline images | Idempotency |
| ---- | ---- | ---- | ----------- | --- | --- | -------- | ------- | ----------- | ------------- | ----------- |
| yes  | yes  | yes  | yes         | yes | yes | one      | yes     | no          | no            | no          |

These fail with `UnsupportedFeatureError` and `acceptance: "notSubmitted"` before any request:

- More than one `replyTo` address (feature `multipleReplyTo`).
- Any attachment (feature `attachments`).
- An `idempotencyKey` (feature `idempotency`).

## Idempotency [#idempotency]

Not supported. A key fails with `UnsupportedFeatureError` before sending.

## Provider notes [#provider-notes]

- MailerSend takes one reply-to address and no attachments through this package. Both fail before sending.
- Header names may contain only letters, digits and hyphens. Any other name fails with `InvalidMessageError` (path `headers`) and `acceptance: "notSubmitted"`.
- A send is accepted only on an HTTP 202 response. If MailerSend reports suppressed recipients, the receipt is `partiallyAccepted` with one outcome per recipient. When every recipient is suppressed the send fails with `MessageRejectedError`.

## Using your own client [#using-your-own-client]

`layerClient` takes any object with `email.send(message)`, which a `MailerSend` client has. `options` is optional. The client must return the response object with `statusCode`, `headers` and `body`, which is what the SDK does.

**Example** (Borrowing a MailerSend Client)

```ts
import { MailerSend } from "mailersend";
import * as MailerSendEmail from "@effect-kit/emails/mailersend";

const client = new MailerSend({ apiKey: "fake-key" });

const EmailLive = MailerSendEmail.layerClient(client);
```

You own a borrowed client. The Layer never closes it, and the client keeps its own retry, timeout and logging policy.

## Errors [#errors]

`ProviderConfigurationError` carries `provider: "mailersend"` and a `field` naming the bad option. Layer construction fails with it, and `layerClient` fails with it for the client options.

| `field`   | Raised when                                        |
| --------- | -------------------------------------------------- |
| `timeout` | The timeout is not finite and positive.            |
| `token`   | The API key is not printable ASCII without spaces. |

| MailerSend failure                        | Reason                                            |
| ----------------------------------------- | ------------------------------------------------- |
| HTTP 202 with an `ALL_SUPPRESSED` warning | `MessageRejectedError` (`acceptance: "rejected"`) |
| A success status other than 202           | `UnexpectedResponseError`                         |

Any other HTTP status uses the shared mapping: 401 is `AuthenticationError`, 403 `PermissionDeniedError`, 429 `RateLimitedError`, 400 and 422 `InvalidMessageError`, 5xx `ProviderUnavailableError`, and anything else `ProviderError`. `acceptance` is `rejected` for a 4xx status other than 409 and `unknown` otherwise. See [Errors](/docs/emails/errors). A network failure with no status is `TransportError`, and `ETIMEDOUT` or `ECONNABORTED` is `TimeoutError`, both with `acceptance: "unknown"`.