The password associated with a user’s account must be entered by the user when he or she authenticates for login or other services. The password is case sensitive (except for SMB-LAN Manager passwords) and is masked on the screen as it’s entered.
Regardless of the password type you choose for a user, here are guidelines for composing a password for OS X Server user accounts:
A password should contain letters, numbers, and symbols in combinations that won’t be easily guessed by unauthorized users. Passwords shouldn’t consist of words. Good passwords include digits and symbols (such as # or $), or they consist of the first letter of all words in a phrase. Use both uppercase and lowercase letters.
Avoid spaces and Option-key combinations.
Avoid characters that can’t be entered on computers the user will use or that might require knowing a special keystroke combination to enter correctly on different keyboards and platforms.
Some network protocols don’t support passwords that contain leading spaces, embedded spaces, or trailing spaces.
A zero-length password isn’t recommended. Open Directory and some systems (such as LDAP bind) don’t support a zero-length password.
For maximum compatibility with computers and services your users might access, use only ASCII characters for passwords.