Messages are not deleted from the forward mailbox
This problem might occur after you have installed the Microsoft Dynamics CRM 4.0 E-mail Router and you have configured the E-mail Router to poll a Microsoft Exchange mailbox for messages to promote into Microsoft Dynamics CRM. Also, the Outlook Web Access Web site is running on Windows Server 2008 with IIS 7.0. You might notice that certain e-mail messages are not deleted from the forward mailbox after the E-mail Router has processed them, even when you have enabled the setting to deleted processed messages.
To fix this problem, run the following command on the IIS 7.0 server, replacing "Default Web Site" with the name of the Web site that needs to be configured:
%windir%\system32\inetsrv\appcmd set config "Default Web Site" -section:system.webServer/security/requestfiltering -allowDoubleEscaping:true