df = pd.DataFrame({'email': ['foo@bar.com', 'bar@bar.com', 'bar@foo.com']})

    email
0   foo@bar.com
1   bar@bar.com
2   bar@foo.com

df['before'] = df.email.str.split('@').str.get(0).str.contains('foo')
df['after'] = df.email.str.split('@').str.get(1).str.contains('foo')



    email       before  after
0   foo@bar.com True    False
1   bar@bar.com False   False
2   bar@foo.com False   True