An Inbox rule may cause the mailbox to expand even if a send limit has been assigned

When you create an Inbox rule that automatically forwards all mail to an external recipient, a loop may occur that causes a mailbox on the server to expand until the server stops. This issue may occur even if there is a send limit on the mailbox.

To resolve this issue, modify the registry in Exchange Server to force Inbox rules to be checked against the mailbox size limits that are placed at the Information Store:

1. Start Registry Editor (Regedt32.exe).
2. Locate and click the following registry key:
   HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeIS\ParametersPrivate
3. Add the following value:
   Value Name: Apply Mailbox Quota to Rules
   Data Type: Reg_DWORD

If this value is not set to 0, messages that are sent according to rules still have the mailbox quota option selected. If the value is not present or is set to 0 (this is the default setting in Exchange Server 5.5 Service Pack 3 [SP3]), messages that are sent according to rules are not affected by the mailbox quota for sending messages.

For additional information, click the article number below to view the article in the Microsoft Knowledge Base:

To work around this issue, add a send and receive limit on the mailbox:

1. Start the Exchange Administrator program.
2. Click the Recipients container for the mailbox.
3. Click Properties, and then click the Limits tab.
4. Click to clear the Use Information Store Defaults.
5. Add an entry in the Prohibit Send and Receive Limit box.

The following scenario is an example of this behavior:

• someone@microsoft.com creates an Inbox rule to forward all mail to someone@expedia.com.
• A message is sent to someone@microsoft.com.
• This message is automatically forwarded to the external address.
• If the recipient of the rule is invalid or if it is over the mailbox limit on the expedia.com domain, then the message generates a non- delivery report (NDR) or an "Invalid E-mail" response.
• This status response is immediately sent back to someone@microsoft.com and the loop is created.

For additional information, click the article number below to view the article in the Microsoft Knowledge Base: