import re

lines = [
        '"mail.com": "bad_domain"\n'
        '"winsecmail.com": "bad_domain"'
        '"win-security-mail.com": "bad_domain"'
        '"win-securitymail.com": "bad_domain"'
        '"www.dhlexpressmail.com": "bad_domain"'
        '"mta5.am0.yahoodns.net": "bad_domain"'
    ]

excluded = [
        "mail.com",
        "imgstatic.eu",
        "mta5.am0.yahoodns.net",
        "static.xx.fbcdn.net"
    ]

pattern = re.compile(r'"(?:%s)"' % '|'.join(excluded).replace(".", r"\."))

for i, line in enumerate(lines):
    for match in re.finditer(pattern, line):
        print(match.group())