export interface MailtrapConfig {
    /**
     * Mailtrap API token used as the Bearer credential.
     */
    apiToken: string;
    /**
     * REQUIRED — explicit, no default. Determines the API endpoint used by `.send()`:
     *   - `'sandbox'`     → `https://sandbox.api.mailtrap.io/api/send/<inboxId>`
     *   - `'production'`  → `https://send.api.mailtrap.io/api/send`
     *
     * No default is provided because the failure mode is asymmetric: a production
     * email accidentally routed to the sandbox is a quiet bug; a sandbox email
     * accidentally hitting production is a real-user-impact bug. Consumers must
     * pick deliberately.
     */
    mode: 'sandbox' | 'production';
    /**
     * REQUIRED when `mode === 'sandbox'`; FORBIDDEN when `mode === 'production'`.
     * Validated synchronously at construction time — misconfigurations throw a
     * `ConnectorError` before the first `.send()` call.
     */
    inboxId?: string;
    from: string;
    senderName?: string;
    fetch?: typeof fetch;
}