# Adapter contract (/docs/reference/adapter-contract)



Custom adapters are plain objects.

```ts
import type { EmailProvider } from "@opencoredev/email-sdk";

export const customAdapter: EmailProvider = {
  name: "custom",
  async send(message, context) {
    const response = await fetch("https://api.example.com/email", {
      method: "POST",
      signal: context.signal,
      body: JSON.stringify(message),
    });

    const body = await response.json();

    return {
      provider: "custom",
      id: body.id,
      raw: body,
    };
  },
};
```

## `EmailProvider` [#emailprovider]

```ts
type EmailProvider<TRaw = unknown> = {
  name: string;
  send(message: EmailMessage, context: EmailProviderContext): MaybePromise<EmailProviderResponse>;
  raw?: TRaw;
};
```

## `EmailProviderContext` [#emailprovidercontext]

| Field            | Type                      | Notes                                          |
| ---------------- | ------------------------- | ---------------------------------------------- |
| `signal`         | `AbortSignal`             | Optional abort signal.                         |
| `idempotencyKey` | `string`                  | Optional key from the message or send options. |
| `attempt`        | `number`                  | Attempt number for this adapter.               |
| `metadata`       | `Record<string, unknown>` | Metadata passed to `send`.                     |

## Adapter responses [#adapter-responses]

```ts
type EmailProviderResponse = {
  id?: string;
  provider: string;
  messageId?: string;
  accepted?: string[];
  rejected?: string[];
  raw?: unknown;
};
```

Return the provider's raw response in `raw` when it helps callers debug or inspect provider-specific fields.