FileStream file1 = new FileStream("accounts.txt", FileMode.Open);
StreamWriter writer = new StreamWriter(file1);
for (int i = 1; i < acc.Count; i++)
{
    writer.WriteLine(acc[i]);
    Console.WriteLine(acc[i]);
}
writer.Close();

example1@example.ex:password1:Origin
example2@example.ex:password2:Origin
example3@example.ex:password3:Origin
example4@example.ex:password4:Origin
example5@example.ex:password5:Origin

example2@example.ex:password2:Origin
example3@example.ex:password3:Origin
example4@example.ex:password4:Origin
example5@example.ex:password5:Origin