# Choosing a provider

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

Compare what each provider supports before you pick one.

Source: https://effectkit.dev/docs/emails/choosing-a-provider

All 16 providers share the `Email` service, but they do not support the same message features. The package checks the message against the provider's capabilities first, and fails with `UnsupportedFeatureError` before any request when a feature is missing.

**Example** (Changing the Provider Without Changing the Program)

```ts tab="Resend" tab-group="provider"
import { Effect } from "effect";
import { Email } from "@effect-kit/emails";
import * as Resend from "@effect-kit/emails/resend";

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(Resend.layerConfig())));
```

```ts tab="Amazon SES" tab-group="provider"
import { Effect } from "effect";
import { Email } from "@effect-kit/emails";
import * as Ses from "@effect-kit/emails/ses";

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(Ses.layerConfig())));
```

```ts tab="Postmark" tab-group="provider"
import { Effect } from "effect";
import { Email } from "@effect-kit/emails";
import * as Postmark from "@effect-kit/emails/postmark";

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(Postmark.layerConfig())));
```

## What differs [#what-differs]

Every provider supports text, HTML, both together, cc, bcc and custom headers, except [Plunk](/docs/emails/providers/plunk). The rest of the differences:

| Provider                  | Reply-to | Attachments | Inline images | Sender name | Idempotency        |
| ------------------------- | -------- | ----------- | ------------- | ----------- | ------------------ |
| `resend`                  | multiple | yes         | yes           | yes         | replay, 24 hours   |
| `nodemailer`              | multiple | yes         | yes           | yes         | no                 |
| `ses`                     | multiple | yes         | yes           | yes         | no                 |
| `azure`                   | multiple | yes         | yes           | no          | no                 |
| `postmark`                | multiple | yes         | yes           | yes         | no                 |
| `sendgrid`                | one      | yes         | yes           | yes         | no                 |
| `mailgun`                 | multiple | yes         | no            | yes         | no                 |
| `mailersend`              | one      | no          | no            | yes         | no                 |
| `brevo`                   | one      | no          | no            | yes         | reject, 30 minutes |
| `mailtrap`                | one      | yes         | yes           | yes         | no                 |
| `scaleway`                | multiple | yes         | no            | yes         | no                 |
| `lettermint`              | multiple | yes         | yes           | yes         | replay, 24 hours   |
| `eusend`                  | multiple | yes         | yes           | yes         | replay             |
| `zeptomail`               | multiple | yes         | yes           | yes         | no                 |
| `mailchimp-transactional` | multiple | yes         | no            | yes         | no                 |
| `plunk`                   | none     | no          | no            | yes         | no                 |

Only Resend, Lettermint, eusend and Brevo support idempotency keys. On any other provider, a message sent with an `idempotencyKey` fails with `UnsupportedFeatureError` before sending. Lettermint inline images need a content id that contains `@`.

<Callout type="warn" title="Plunk is HTML only">
  Plunk sends HTML with exactly one `to` address and no name. It has no text body, cc, bcc,
  reply-to, headers or attachments, so any of those fail with `UnsupportedFeatureError`.
</Callout>

Read these at runtime from `email.capabilities`, and see the [provider overview](/docs/emails/providers) for the full matrix.