Various performance issues occur when you use Entourage for Mac to send large e-mail messages to an Exchange 2007 server

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SYMPTOMS

You use a Microsoft Entourage for Mac client to connect to a mailbox that is located on a server that is running Microsoft Exchange Server 2007. If Entourage for Mac sends a message that has an attachment that exceeds the send size limitation in Exchange 2007, the mailbox store becomes unstable. Additionally, you experience one or more of the following symptoms:

Transaction logs are generated.
The average remote procedure call (RPC) latency spikes to more than 1,000 milliseconds (msec). Sometimes the average RPC latency spikes to more than 20,000 msec.
CPU usage spikes from 25 percent to 50 percent. Sometimes, CPU usage nears 100 percent.
If a Microsoft Office Outlook client is also installed on the computer, you receive an RPC latency dialog box in Outlook. Additionally, Outlook does not work until the Microsoft Exchange Information Store service is restarted.
You receive the following error message in Entourage for Mac:
An unknown error (-18493) has occurred. Your mailbox has exceeded the size limit. Account name: "Your_Username".
Note The e-mail message is then moved to the Drafts folder. Every time that Entourage for Mac tries to perform a regular synchronization with Exchange 2007, Entourage for Mac stops responding for several minutes when it tries to synchronize the Drafts folder. Additionally, lots of disk thrashing occurs on the Macintosh computer.

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WORKAROUND

To work around this problem, modify the value in the MaxRequestEntityAllowed property to restrict the transmission of large amounts of data. To do this, follow these steps:

Save a backup file of the Metabase.xml file in the following directory:
%windir%\system32\inetsrv
In Service Control Manager, stop the IIS Admin Service service.
Open the Metabase.xml file in the %windir%\system32\inetsrv folder in Notepad.
Locate the Exchange Virtual directory section.

Add the MaxRequestEntityAllowed property that contains the largest file size upload that you want to allow. Add this property under the LogonMethod property, and then save the file.

The following is the MaxRequestEntityAllowed property syntax:

MaxRequestEntityAllowed=”Size in bytes”

Note Size in bytes is the largest file size upload that you want to allow. The following is an example of the size:

MaxRequestEntityAllowed="31457280"

In the following example the maximum file size upload is set to 30 MB:

<IIsWebVirtualDir    Location ="/LM/W3SVC/1/ROOT/Exchange"
                  AccessFlags="AccessSource | AccessRead | AccessWrite"
                  AppFriendlyName="Exchange"
                  AppIsolated="2"
                  AppPoolId="MSExchangeOWAAppPool"
                  AppRoot="/LM/W3SVC/1/ROOT/Exchange"
                  AuthFlags="AuthBasic"
                  DirBrowseFlags="EnableDirBrowsing | DirBrowseShowDate | DirBrowseShowTime | DirBrowseShowSize | 
DirBrowseShowExtension | DirBrowseShowLongDate | EnableDefaultDoc"
                  DoDynamicCompression="FALSE"
                  DoStaticCompression="TRUE"
                  LogonMethod="3"
                  MaxRequestEntityAllowed="31457280"
                  Path="\\.\BackOfficeStorage\tx1b46bdomain.com\MBX"
                  ScriptMaps="*,C:\Program Files\Microsoft\Exchange Server\Bin\exprox.dll,1"
>

Start the IIS Admin Service service in Service Control Manager.

Note Do not set the MaxRequestEntityAllowed property in any virtual directory other than the Exchange Server virtual directory. For example, if you set this property in the virtual root directory to a file size that is less than 1 GB, RPC over HTTP logon issues occur. Make sure that you set this property on all Exchange Server 2007 mailbox servers and on all Exchange Server 2007 Client Access Server (CAS) servers.

Be aware that if you set the MaxRequestEntityAllowed property on the CAS server, the CAS server returns an error message that states that the request to send a large e-mail message failed. This behavior is expected.

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