A user can still send or receive e-mail messages successfully after you set a message size delivery restriction to 0 KB for an Exchange Server 2003 mailbox

After you set a Sending message size delivery restriction or a Receiving message size delivery restriction to 0 KB for a particular mailbox-enabled user, that user can still send or receive e-mail messages successfully.

You expect these delivery restrictions to prevent the user from sending or receiving e-mail messages.

You experience this issue if the user has a mailbox that is hosted on a Microsoft Exchange Server 2003-based server.

Note To view the options to configure delivery restrictions, follow these steps:

1. Start the Active Directory Users and Computers tool.
2. Right-click the user account for which you want to view delivery restrictions, and then click Properties.
3. Click the Exchange General tab, and then click Delivery Restrictions.

This issue occurs because of how Exchange 2003 interprets a value of zero in a message size delivery restriction.

In Exchange 2003 and in earlier versions of Exchange, a delivery restriction of zero corresponds to an unlimited message size. Therefore, if you set a Sending message size delivery restriction or a Receiving message size delivery restriction to 0 KB, you effectively allow for an unlimited message size for delivery or for receipt.

Note In Microsoft Exchange Server 2007, a message delivery restriction of 0 KB restricts messages to 0 KB. Therefore, no messages may be sent or received, as appropriate for the particular setting.

To work around this issue, use a low nonzero number, such as one, to set the delivery restrictions. A low message size limit, such as 1 KB, may help stop the user from sending or receiving e-mail messages.

Warning If you use the ADSI Edit snap-in, the LDP utility, or any other LDAP version 3 client, and you incorrectly modify the attributes of Active Directory objects, you can cause serious problems. These problems may require you to reinstall Microsoft Windows 2000 Server, Microsoft Windows Server 2003, Microsoft Exchange 2000 Server, Microsoft Exchange Server 2003, or both Windows and Exchange. Microsoft cannot guarantee that problems that occur if you incorrectly modify Active Directory object attributes can be solved. Modify these attributes at your own risk.

In Exchange 2003, the submissionContLength attribute value and the delivContLength attribute value are set to zero in the Active Directory directory service when you set the corresponding maximum message size to 0 KB in a message size delivery restriction. To view these attributes, follow these steps:

1. Start the ADSI Edit tool. To do this, click Start, click Run, type adsiedit.msc, and then click OK.
   
   Note The ADSI Edit tool is included together with Windows Support Tools. To install Windows Support Tools on a computer that is running Microsoft Windows 2000 Server, double-click Setup.exe in the Support\Tools folder on the Windows 2000 Server CD. To install Windows Support Tools on a computer that is running Windows Server 2003, double-click SUPTOOLS.MSI in the Support\Tools folder on the Windows Server 2003 CD.
2. Connect to a domain controller if the ADSI Edit tool is not already connected to a domain controller.
3. Expand Domain NC [servername.example.com], expand DC=example,DC=com, and then click the container in which the user account is located. For example, click CN=Users or click OU=UserContainer.
4. Right-click the user account object for which you set the message size delivery restriction to 0 KB, and then click Properties.
5. In the Select a property to view list, click submissionContLength. Notice that 0 appears in the Value(s) box.
6. In the Select a property to view list, click delivContLength. Notice that 0 appears in the Value(s) box.
7. Click Cancel, and then exit the ADSI Edit tool.