email-domain-check/dist/esm/mta-sts.js

Comprehensive email domain validation library with DNS, MX, SMTP, DKIM, DMARC and MTA-STS support.

import { Address, IPKind } from './address.js';
export async function getMtaStsPolicy(target) {
    const addr = Address.loadFromTarget(target);
    if (addr.ipKind !== IPKind.None) {
        return null;
    }
    try {
        const url = `https://mta-sts.${addr.hostname}/.well-known/mta-sts.txt`;
        const response = await fetch(url, {
            method: 'GET',
            headers: {
                'User-Agent': 'email-domain-check',
            },
            signal: AbortSignal.timeout(8000),
        });
        if (!response.ok) {
            return null;
        }
        const text = await response.text();
        return parseMtaStsPolicy(text);
    }
    catch {
        return null;
    }
}
export function isMxAllowed(mxHost, policy) {
    return policy.mx.some((pattern) => {
        if (pattern.startsWith('*.')) {
            // Wildcard match: *.example.com
            const suffix = pattern.slice(1); // .example.com
            return mxHost.endsWith(suffix);
        }
        else {
            // Exact match
            return mxHost === pattern;
        }
    });
}
function parseMtaStsPolicy(policyText) {
    const lines = policyText
        .split('\n')
        .map((line) => line.trim())
        .filter((line) => line && !line.startsWith('#'));
    const policy = {
        mx: [],
    };
    for (const line of lines) {
        const [key, value] = line.split(':').map((s) => s.trim());
        if (!key || !value)
            continue;
        switch (key.toLowerCase()) {
            case 'version':
                policy.version = value;
                break;
            case 'mode':
                if (value === 'enforce' || value === 'testing' || value === 'none') {
                    policy.mode = value;
                }
                break;
            case 'mx':
                policy.mx?.push(value);
                break;
            case 'max_age':
                policy.max_age = parseInt(value, 10);
                break;
        }
    }
    if (policy.version && policy.mode && policy.mx && policy.max_age !== undefined) {
        return policy;
    }
    return null;
}