id          email         created_at
0  1   son@mail_a.com   2017-01-21 18:19:00
1  2   boy@mail_b.com   2017-01-22 01:19:00
2  3  girl@mail_c.com   2017-01-22 01:19:00

mail_a.com
mail_d.com
mail_e.com

email_domains = open('file.txt', 'r')
to_drop = email_domains.read().splitlines()
dropped_df = test_df[~test_df['email'].isin(to_drop)]
    print(test_df)

id          email         created_at
0  2   boy@mail_b.com   2017-01-22 01:19:00
1  3  girl@mail_c.com   2017-01-22 01:19:00