Y.Turner@Hotmail.Com:Yvette Turner
Kelliekelly@Hotmail.Com:Kellie Kelly
Hades2056@Hotmail.Com:James Gillam
Peter.Garrad@Tesco.Net:Carl Garrad

Hades2056@Hotmail.Com
Peter.Garrad@Tesco.Net

file_1 = open('1.txt', 'r').read().split('n')
file_2 = open('2.txt', 'r').read().split('n')

array = []
for email in file_1:
    if email.split(':')[0] not in file_2:
        array.append(email)

str = ""
for email in array:
    str += email
    str += 'n'

file_3 = open('3.txt', 'w')
file_3.write(str)