/**
 * @module
 * Duck-typed wiring for RetryTransport / FallbackTransport sender hooks.
 * Kept separate so channel senders do not import the decorator modules.
 */
/** Transport that accepts per-send retry callbacks. */
export interface RetryHookTransport {
    setMailerOnRetry(callback: ((attempt: number, error: unknown) => void) | undefined): void;
}
/** Transport that accepts per-send fallback callbacks. */
export interface FallbackHookTransport {
    setMailerOnFallback(callback: ((failedProvider: string, nextProvider: string, error: unknown) => void) | undefined): void;
}
/** True when the transport exposes {@link RetryHookTransport.setMailerOnRetry}. */
export declare function isRetryHookTransport(transport: unknown): transport is RetryHookTransport;
/** True when the transport exposes {@link FallbackHookTransport.setMailerOnFallback}. */
export declare function isFallbackHookTransport(transport: unknown): transport is FallbackHookTransport;