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,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 that is over the attachment size limit is moved to the Drafts folder. Every time that Entourage for Mac tries to perform a regular synchronization with Exchange 2007, Entourage for Mac crashes for several minutes when it tries to synchronize the Drafts folder. Additionally, lots of disk thrashing occurs on the Macintosh computer.
Increasing the allowed attachment size may cause performance issues in the Exchange environment. You have to consider the increase load a large attachment puts on the server infrastructure. You may experience one or more of the following symptoms if the attachment size is increased:
The Mailbox store database may become unstable.
High numbers of transaction logs are generated.
The average remote procedure call (RPC) latency spikes to more than 1,000 milliseconds.
Occasionally the average RPC latency spikes to more than 20,000 milliseconds.
CPU usage spikes from 25 percent to 50 percent. Occasionally, 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.
The procedure to control attachment sizes for Entourage for Mac varies based on the version that you are using. Please follow the correct procedure for the version that you are using. You have to make these changes on all Exchange 2007 client access role servers that Entourage for Mac client connects to.
Exchange 2007 and Exchange Server 2010: Microsoft Entourage 2008 for Mac, Web Services Edition, Microsoft Outlook 2011 for Mac
1. This version of Entourage for Mac uses the Microsoft Exchange Server 2007 Web services provider to send mail. To allow for larger attachments that you must change the MaxRequestLength in the web.config file. By default, the web.config file is located in the EWS Virtual directory Microsoft\Exchange Server\ClientAccess\exchweb\EWS will have the following entry, by default, the max request size is approximately 13MB
Change the item <httpRuntime maxRequestLength="13280" /> to <httpRuntime maxRequestLength="X" /> where X is the desired value in KBs. for example, X will be approximately 50000 (50MB).
Exchange Server 2003 and Exchange Server 2007: Microsoft Entourage 2004 or Microsoft Entourage 2008, for Mac
This version of Entourage for Mac used WebDav to connect to Microsoft Exchange Server 2007. To allow larger attachment sizes you must change the MaxRequestEntityAllowed property in the IIS Metabase.xml file. 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:
In the following example the maximum file size upload is set to 30 MB:
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.
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.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.