Microsoft KB Archive/169205

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Knowledge Base

XADM: Repercussions of Deleting Public Folder Replication Messages

Article ID: 169205

Article Last Modified on 10/28/2006


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

This article was previously published under Q169205


This article explains the repercussions of deleting public folder replication messages from the MTA queues using the Exchange Administrator program or the Mtacheck.exe utility with the /rp option.


To resolve a backlogged MTA, it may be necessary to remove all public folder replication messages in the MTA queues. When this is done, the result may be the generation of even more public folder replication messages, which may exacerbate the MTA problem.

During normal public folder replication, when a change is made to one of the replicas of a public folder, the change is sent out to all the other servers that have replicas of that public folder. This change is sent out as a single mail message addressed to the public information store on each server, in each of the other sites in the organization. The MTA is responsible for routing this message to the correct destinations.

When public folder replication messages in the MTA queues are removed, these regular public folder messages are not received by the destination servers. Eventually, the other servers will generate backfill request messages asking the server with the changes to send them the changes. These changes are now individually sent to each server requesting a backfill, and in turn, the number of public folder replication messages generated are larger.

Consider a Microsoft Exchange organization with 20 sites with public folder replicas on one server in each site. If a public folder on a server in Site 1 is modified, public folder replication messages are sent out to all other servers in the other sites that contain a replica of this public folder.

Now, suppose the MTA on the bridgehead server in Site 1 is backlogged and all the public folder replication messages in the MTA queues to the other sites are removed. When this is done, the public folder replication messages containing the changes to the public folder in Site never reach the other sites. This causes the servers in the other sites to generate Backfill request messages requesting these changes. In response to these Backfill messages, another message is sent to each server requesting the changes. This results in an individual message being sent to each server in the other sites containing a replica of the public folder. As a result, the MTA queues to the other sites will now have 19 new messages instead of the one original message which was deleted from the queue. This is in addition to the traffic generated by the Backfill messages from each of the other servers.

In a large organization with several sites and several servers in each site, the amount of additional traffic caused by public folder backfill requests can be significant. Therefore, you should use caution when you use the MTACHECK utility with the /rp option or delete public folder replication messages.

Keywords: kbinfo KB169205