Why can’t I do a Deep Traversal (subfolder) Search on the MAPI Public Folder Tree?


I am sure many of you have at one time or another wanted to do a Deep Traversal (subfolder) Search on the MAPI Public Folder Tree.  However, as many of you probably know, Exchange does not allow for Deep Traversal (subfolder) Searches on the MAPI Public Folder Tree: http://support.microsoft.com/default.aspx?scid=kb;en-us;254911.  The reason you cannot do this is because when the Public Folder system was designed, it was decided that load balancing would be accomplished by putting only some of the content on some of the servers. For example, if there exists 3 folders and 3 servers. Folder1 may be replicated between servers 1 & 2, folder2 between servers 2 & 3, and folder3 between 1 & 3. If the client created a search folder that simultaneously searched all three folders, they’d get different results depending on which actual Public Folder Server they were connected to. To address this issue, search folders cannot be created that search the content of multiple folders; deep traversal, or subfolder, being a special case of “multiple folders”.



One way to get around this “limitation” is by setting up a Non-MAPI Public Folder Tree because you can do a Deep Traversal (subfolder) Search against that: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/e2k3/e2k3/_exch2k_specifying_a_deep_traversal.asp?frame=true.  However, you cannot view this Public Folder Tree via MAPI (i.e Outlook).  So what is the difference you ask?  Well, the thought behind Application Public Folder Stores was that, for the most part, the content of the folders would not be replicated to any other server. There’s no actual architectural limitation to enforce this – Exchange originally just foresaw organizations would create only one Application Public Folder Store at all and so replication wouldn’t be an issue. Therefore, users can create Search Folders that can search the content of multiple folders. Given this, though, you do actually step back into the original problem. Namely, the search folder itself is replicated among servers but the content is always generated locally. Also, clients are never referred to a different server – search folders always seem (to the client) to have their exclusive replica on the server presently being queried. So, users should be aware that they will get different results depending on which server they contact for the content, and of course replication latency adds a new dimension to the differing results.


- Chris Ahlers

Comments (5)
  1. Scott Bueffel says:

    Chris, I assume that even doing an FTI of a public store still does not allow for subfolder searching, correct? Are there any third-party solutions that will do this against a public store/hierarchy? Some have suggested Sharepoint. Is it true I can have Sharepoint target a PF hierarchy and index it, independent of the actual folder content location? As part of our email retention policy we are moving documents, etc., to PFs and the clients REALLY want/need to be able to search subfolders.

    Scott Bueffel

  2. Chris Ahlers says:

    Scott–

    You are correct about the Full-Text Index (FTI).

    As far as third-party solutions go, the only one that I am currently aware of is Sharepoint (http://www.microsoft.com/sharepoint/default.asp). So to answer your question, yes Sharepoint will allow you to index the content of your Public Folders. The following web page talks about indexing Exchange Public Folder content with SPS: http://www.microsoft.com/technet/prodtechnol/office/sps2003/maintain/crawle55.mspx. I know it talks about indexing Exchange 5.5, but further down it gets to Exchange 2000 (2003 will be the same.) I hope this helps.

    –Chris

  3. Nick Wade says:

    Your other choices include archiving the public folder stores into a nearline system that includes a decent index / FTI. Try KVS as a good starting point – I work there and would say that, but you’ll find that KVS are Microsoft’s key GTM partner around archiving for FY05.(http://directory.partners.extranet.microsoft.com/SolutionPage.aspx?i=41&cat=0&SolutionID=2364&pid=5&vid=0)

  4. Nick Wade says:

    Anyway – who cares? MSFT gave MSN the money and go ahead and buy (http://www.investors.com/breakingnews.asp?journalid=22179418&brk=1) Lookout (http://www.lookoutsoft.com). As it’s gonna be indexing content in Outlook, pub folders, imap folders, PST files, Outlook Express and probably Hotmail folders, I wouldn’t worry too much about being unable to search when Longhorn comes along (and has this embedded)

    Cheers

  5. Nick Wade says:

    Oops, bugger me because I forgot that it also indexed files on your PC as well… :-)

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