XADM: Unable to Reply All to Forwarded Post from a Public Folder

After applying Exchange Server 5.5 Service Pack 2 (SP2), users who receive forwarded posts from public folders will not be able to do a Reply-all. The message remains a post during the forward process, and the only valid operations are Reply, Forward, and Post-reply.

Changes were made in Exchange Server 5.5 SP2 to preserve the message class for forwarded messages when the "Leave message intact" method is used with a Folder Assistant rule. For additional information, please see the following article in the Microsoft Knowledge Base: Previously, a post (IPM.Post message class) was changed to a note (IPM.Note message class) during the forward operation. Changing the message class can prevent forms from working on forwarded messages. Exchange Server 5.5 SP2 corrected this problem by preserving the message class during the forward.

Some customers were relying on this transformation of the message class from IPM.Post to IPM.Note to allow MAPI clients to Reply-all to these forwarded posts. For these customers, the changes made in Exchange Server 5.5 SP2 prevent the client from working as they anticipated.

To resolve this problem, obtain the latest service pack for Exchange Server version 5.5. For additional information, click the following article number to view the article in the Microsoft Knowledge Base: The English version of this fix should have the following file attributes or later:

Component: Store

Microsoft has confirmed that this is a problem in Exchange Server version 5.5 Service Pack 2. This problem was first corrected in Exchange Server 5.5 Service Pack 3.

The default behavior of this new information store is to preserve the message class for forwarded messages. If you wish to revert the server to performing the transformation of the message class, then you must install this fix, and specify a new registry value.

WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

1. Run Registry Editor (Regedt32.exe).
2. Go to the following key in the registry:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\ParametersPublic
3. On the Edit menu, click Add Value, and use the following entry:
   Value Name: Enable Old Forward Method
   Data Type: REG_DWORD
   Value: 1
4. Exit the Registry Editor, and restart the information store service for the change to take effect.

Setting the registry value to 0 (or removing it) restores Exchange Server 5.5 to preserving the message class during the forward operation.