Domain Controller has following Policy.
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Minimum / Maximum Password Age :- Not Defined.
Complexity :- Disabled
History :- Disabled:-
Length :- 2 Characters.
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Users are able to change the password, when "Change password at next logon is selected". However if user tries to change the password again, windows does not allows to change the password & it gives error :- Unable to update password Please check complexity history length etc.. etc..