A valid password should be a mix of upper and lower case letters, digits, and other characters. You can use a 7 character long password with characters from at least 3 of these 4 classes.
An upper case letter that begins the password and a digit that ends it do not count towards the number of character classes used.
The user name can be invalid if it contains a special character.
The password can be invalid if it does not contain a letter, a number, and a special character.