Good news! Exchange Server 2007 Service Pack 3 and Exchange Server 2010 Service Pack 1, running on Windows Server 2008 or Windows Server 2008 R2 have a new feature that will allow users with expired passwords to change their password. This also works for users with the User must change password at next logon specified on their AD account.
Read more at source: http://msexchangeteam.com/archive/2010/10/06/456520.aspx
You can also check here at MSExchange.org my article about Exchange Server 2007 SP3 and all the required steps are described there as well, here is the link: http://www.msexchange.org/articles_tutorials/exchange-server-2007/management-administration/deploying-exchange-server-2007-service-pack3.html
Cheers,
Anderson Patricio
http://blogs.msexchange.org/patricio
Twitter: @apatricio
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