/w+@(tickets.)?company.com/i

findall(pattern, string, flags=0)
    Return a list of all non-overlapping matches in the string.

    If one or more groups are present in the pattern, return a
    list of groups; this will be a list of tuples if the pattern
    has more than one group.

    Empty matches are included in the result.

r'(w+@(tickets.)?company.com)'
r'w+@(?:tickets.)?company.com'

'(w+@(?:tickets.)?company.com)'

r'w+@(tickets.)?company.com'

>>> import re
>>> exp = re.compile(r'w+@(tickets.)?company.com')
>>> bool(exp.match("s@company.com"))
True
>>> bool(exp.match("1234567@tickets.company.com"))
True

#!/usr/bin/python

import re

regex = re.compile("(w+@(?:tickets.)?company.com)");

a = [
    "foo@company.com",
    "foo@tickets.company.com",
    "foo@ticketsacompany.com",
    "foo@compant.org"
];

for string in a:
    print regex.findall(string)