http://blogs.msdn.com/mstehle/archive/2009/06/24/fyi-can-t-use-exchange-impersonation-with-getuseroofsettings-setuseroofsettings-or-getuseravailability.aspxI kept forgetting about this so maybe blogging it will help me remember.&#160; As this thread confirms – you can’t call GetUserOofSettings, SetUserOofSettings, or GetUserAvailability when using Exchange Impersonation.&#160; If you try to do this you’llen-USCommunityServer 2.1 SP1 (Build: 61025.2)http://blogs.msdn.com/mstehle/archive/2009/06/24/fyi-can-t-use-exchange-impersonation-with-getuseroofsettings-setuseroofsettings-or-getuseravailability.aspx#9802106Wed, 24 Jun 2009 23:51:05 GMT91d46819-8472-40ad-a661-2c78acb4018c:9802106Vikas Verma<p>and you might want to include this in your thread :)</p> <p><a rel="nofollow" target="_new" href="http://blogs.msdn.com/vikas/archive/2009/05/29/howto-ews-get-oof-state-for-self-or-any-user-in-your-organization.aspx">http://blogs.msdn.com/vikas/archive/2009/05/29/howto-ews-get-oof-state-for-self-or-any-user-in-your-organization.aspx</a></p>