Microsoft KB Archive/169704

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Article ID: 169704

Article Last Modified on 10/27/2006


  • Microsoft Exchange Server 5.5 Standard Edition
  • Microsoft Exchange Server 5.0 Standard Edition

This article was previously published under Q169704


A mailbox on Microsoft Exchange Server may grow very large; its expansion is limited only by available disk space. This can occur when a rule has been created that forwards mail to an address where another agent causes mail to be returned to the user. This cycle results in a continuous flow of mail between the automatic agents, expanding the mailbox.


Microsoft Exchange Server version 5.0 does not check mailbox limits if the mail message is generated by a rule. This allows the automatic mail to continue indefinitely, consuming disk resources and generating excessive mail traffic. Mailbox size limits are checked when the mail is user- generated.


Microsoft has confirmed this to be a problem in Microsoft Exchange Server version 5.0. This problem has been corrected in the latest U.S. Service Pack for Microsoft Exchange Server version 5.0. For information on obtaining the service pack, query on the following word in the Microsoft Knowledge Base (without the spaces):



NOTE: In Exchange Server version 5.5 Service Pack 3 a rule can start regardless of the mailbox or public folder quota limits. This was first changed to correct the situation in which meeting requests are not delivered if the recipient mailbox is full. For additional information about that situation, click the article number below to view the article in the Microsoft Knowledge Base:

217139 XADM: Meeting Requests Are Not Delivered if Recipient's Mailbox Has Exceeded the Storage Limit and Has a Delegate Defined

However, you can create the following registry key to troubleshoot a rapidly growing information store on an Exchange Server 5.5 Service Pack 3 computer:


Value Name: Apply Mailbox Quota to Rules
Data Type: Reg_DWORD

If this value is not 0, messages sent by rules still have the mailbox quota checked. If the value is not present or is 0 (the default in Service Pack 3), messages sent by rules ignore the mailbox quota for sending messages.

IMPORTANT: If you set mailbox quotas to rules, there may be side effects. For example, if you set a forward and delete rule, it may result in data loss, and if you set meeting requests to go only to the delegate, neither may receive the request if the mailbox is over the limit.

Additional query words: full office service provider loop

Keywords: kbbug kbfix kbusage KB169704