gistfile1.txt

#!/usr/bin/python
import sys
import dns.resolver

resolver = dns.resolver.Resolver()
resolver.timeout = 5
resolver.lifetime = 5

if __name__ == '__main__':
    source_file = sys.argv[1]
    with open(source_file) as infile, open('result_MX.txt', 'wb') as outfile:
        for domain in infile:
            domain = domain.strip()
            print('Getting MX records for: %s' % domain)
            try:
                answers = resolver.query(domain, 'mx')
                outfile.write(domain + '\n')
            except:
                pass