One of my clients where we had deployed Exchange 2007 called me the other day with a complaint that his users could not change their passwords from Outlook Web Access.

Each time they tried to change their password, OWA would throw back "Password does not meet the complexity requirments, please contact your administrator".

This would happen no matter how long / short / complex / simple you made the password. Even more interesting was the fact that there was no complexity required in the domain GPO and the minimum password length set to only 3 characters.

I was puzzled for ages on this and eventually stumbled accross something - it appears this behaviour is caused by the Minimum Password Age setting in the Domain GPO. If you do not enable a minimum password age then OWA will not let you change the password.

Solution: Enable the Minimum Password Age setting and set it to 0 or higher for the Change Password feature of OWA to work.