Error setting Out of Office via Outlook during Exchange 2010/2013 Coexistence
Recently we implemented Exchange 2013. During the CoExistence period we experienced an issue with external users (accessing via Internet) not being able to set their OoO rule. This only seemed to affect those users whos mailbox still resided on the old 2010 Exchange server. The solution turned out to be one of those that you would never have stumbled upon and was only found because somebody else posted the exact same issue. After raising a case with MS and spending 48hr talking to support (not continually I suspect) the following solution was implemented On E2k13 CAS server IIS manager. Highlight EWS virtual directory and select Configuration Editor In the drop down, select System.WebServer/ServerRuntime/ Then in the middle pane select UploadReadAheadSize and set it to 49152 Do an IISReset Hope this helps somebody else Ref: http://social.technet.microsoft.com/Forums/exchange/en-US/c5f80b3f-c73d-4911-b734-c9e846642bfa/exchange-2013-sp1-coexistence-exchange-2010-sp3-roll