export interface SparkPostConfig {
    /** SparkPost API key (sent verbatim in `Authorization` header — no `Bearer` prefix). */
    apiKey: string;
    /** Default `from` address. */
    from: string;
    /** Optional sender name applied alongside `from`. */
    senderName?: string;
    /**
     * SparkPost region. `'us'` (default) routes to `https://api.sparkpost.com`;
     * `'eu'` routes to `https://api.eu.sparkpost.com`.
     */
    region?: 'us' | 'eu';
    /** BYO fetch hook — defaults to `globalThis.fetch`. */
    fetch?: typeof fetch;
}