/**
 * Cogent Mail F3 — recognize a mailbox AUTHENTICATION failure from either mail library, so the
 * send/fetch tools can surface an ACTIONABLE hint (NOT to self-clear creds — a mail-protocol auth
 * denial is wire-indistinguishable between a reversible admin SUSPEND and a reap-delete, and wiping
 * still-valid creds on a suspend would permanently lock the agent out after it's resumed; a genuine
 * reap already clears creds via the deregister deprovision-header path).
 *
 * Signatures verified against the libraries (do NOT broaden blindly — a transient network/timeout
 * error must NOT be mistaken for a credential failure):
 *  - **imapflow** throws `AuthenticationFailure extends Error` with `authenticationFailed: true`
 *    (+ optional `serverResponseCode`, e.g. "AUTHENTICATIONFAILED"). [imapflow _autodocs/errors.md]
 *  - **nodemailer** SMTP auth failure sets `code: "EAUTH"` and `responseCode: 535`
 *    (the "535 5.7.8 authentication failed" reply). [nodemailer SMTP error contract]
 */
export declare function isMailAuthError(err: unknown): boolean;
/**
 * The actionable suggestion to attach to a mailbox auth failure. Deliberately does NOT tell the agent
 * to re-run cogent_setup_mail unless the box was actually deleted — a suspend is temporary and the
 * SAME creds work again after an admin resumes the box.
 */
export declare function mailAuthErrorHint(): string;
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