import re

from dns.rdatatype import MX as rdtype_mx
from dns.resolver import Answer, resolve

HOST_PATTERN = re.compile(
    # max length for domain name labels is 63 characters per RFC 1034
    r'((?:[A-Z0-9](?:[A-Z0-9-]{0,61}[A-Z0-9])?\.)+)'
    r'(?:[A-Z0-9-]{2,63}(?<!-))\Z', re.IGNORECASE)


def get_MX_records_by_email(email, timeout=10):
    _, domain = email.split('@', 1)
    
    try:
        answer = resolve(
            qname=domain,
            rdtype=rdtype_mx,
            lifetime=timeout,
            search=True
        )
    except Exception:
        return None
    
    result = list()

    for record in answer.rrset.processing_order():
        dns_str = record.exchange.to_text().rstrip('.')
        if dns_str in result:
            continue
        if HOST_PATTERN.search(string=dns_str):
            result.append(dns_str)
    return result or None