We are currently running a mix enviroment Exchange 2003/2007. My users on the 2007 box receive the following error on some public folder in OWA. "Click here to open this folder with Microsoft Exchange 2003 Outlook Web Access." Any ideas?

You'll see that if the replica is on the 2003 server and not on the 2007 server.

How do i setup the replica on the 2007 box?

How do i setup the replica on the 2007 box? Well, the easist way is to simply open the Public Folder Mgmt MMC in the EMC toolbox, go to the properties of the folder and add the replica there - or use powershell. If you need to start the process to replicate all the 2003 folders to 2007 see: http://blogs.technet.com/b/exchange/archive/2007/06/25/3403244.aspx Administration of Public Folders with the introduction of Exchange 2007 http://technet.microsoft.com/en-us/library/bb124411(EXCHG.80).aspx

Yes this issue can be caused by the public folder replica related issue. please add the replica and wait for enought time till the replication finishes, and then try again to see if this works. Refer to: Managing Public Folder Replication http://technet.microsoft.com/en-us/library/bb629631(EXCHG.80).aspx Fiona