import { z } from 'zod';
export declare const attachmentSchema: z.ZodObject<{
    filename: z.ZodEffects<z.ZodString, string, string>;
    mimeType: z.ZodString;
    content: z.ZodString;
}, "strip", z.ZodTypeAny, {
    content: string;
    mimeType: string;
    filename: string;
}, {
    content: string;
    mimeType: string;
    filename: string;
}>;
export type Attachment = z.output<typeof attachmentSchema>;
/**
 * RFC 2047 encoding for header values (e.g. Subject). Headers must be ASCII;
 * raw UTF-8 gets mojibaked by Gmail (an em dash becomes "—"). Values that
 * are already ASCII pass through untouched.
 */
export declare function encodeHeaderValue(value: string): string;
/**
 * Quoted-printable encoding (RFC 2045) with soft line breaks. Without a
 * Content-Transfer-Encoding, Gmail hard-wraps long lines at ~72 chars when it
 * ingests a raw message — mid-paragraph breaks the author never wrote.
 * Soft breaks (`=\r\n`) disappear on decode, so paragraphs survive intact.
 */
export declare function quotedPrintableEncode(text: string): string;
/**
 * Appends MIME multipart body with attachments to an array of RFC 2822 header lines.
 * If no attachments, appends the body part on its own.
 */
export declare function appendMimeBody(lines: string[], body: string, attachments?: Attachment[], htmlBody?: string): void;