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Archive Mailbox is Caching to Local Machine

  • I'm having an issue that where my online archive mailbox is caching to my local machine.  I've tested on several machines and have the same experience on all machines.  In previous research I came across this posting (, which suggests a registry entry.  I've tried the registry entry, but this hasn't fixed the issue.  Also, please note this is a purely Office 365 environment with no on-premise servers. 

    I need to get this working as I have several users with near 20GB mailboxes and I'd prefer to use the retention policies to only keep the past 1 year of email in the mailbox and move everything else to the online archive.  I have the retention policies properly moving 1+ year old items to the archive, but then the archive just gets downloaded to the local machine.  This seems to partially defeat the purpose of the online archive.

    Also, I opened a ticket with support regarding this and they said the only way this is possible is to make a registry edit on the server itself, but this is obviously not possible considering the shared nature of the Microsoft servers.

    Any ideas on how to get this functional would be greatly appreciated.  If its not possible than recommendations on 3rd party providers that have working archive solutions would be great.

  • Hi HTech,

    How are you connecting to the Archive mailbox? Have you created a new profile for the box? If you are using Outlook 2010, have you added the mailbox to your default profile?

    If so, you may want to make sure you are connecting to the mailbox without using Cached Exchange Mode.

    You can also connect to the archive mailbox using OWA, which would not download a copy to the computer.

    Let me know if that helps,


  • Hi Dave,

    The mailbox is setup as the default profile in Outlook 2010 with Cached Mode turned on.  Prior to posting this question we found that unchecking the cached mode option would stop the downloading of the email locally, but that doesn't help much.  Ideally we want the regular mailbox cached for faster email searches in outlook and within the Windows 7 search dialog.  However we don't need the archive cached as these are old emails that don't need to be searched very often, but still need to be accessible.

    It seems odd to me that the only options are to have everything fully cached or nothing cached.  With Microsoft offering enterprise archive mailboxes starting at 100GB, I can't understand who'd want cache something that large to their local machine.  Where as it makes a good deal of sense to cache your primary mailbox for faster searching and email retrieval with our without a connection to the exchange server.

    Anyways, I appreciate the suggestions.



  • Please take a close look at Proofpoint.  Leading 3rd party archiving provider for BPOS and Office 365 customers in the Enterprise space.  We provide tight technical integration with on premise Exchange 03/07/10 and Office 365.

    Email me if you have questions.  Cheers! 

    Dave Huth

  • HTech,

    I spent the weekend testing this and I can't find any way to seperate the archive mailbox from the regular mailbox. Since the Archive mailbox is part of the mailbox, the caching feature can't be turned off independently.

    The only other option in Office 365 would be to create another mailbox and forward a copy of each email to that mailbox, but that would be limited to 25 GB and would require a second license.

    Otherwise, the only way I can think of doing this is to use a third party archiving solution.


  • Thanks David!  That's what I needed to know.

  • David and HTech,

     When you were investigating this what whas your test methodology?  I too am interested in this question but as far as I can tell it does work the way you want it to.

    Here's how I tested it:

    I am using Outlook 2010 in cached mode with an E1 level account.

    I added an archive to the mailbox and it eventually showed up in Outlook.

    I sent several large attachments to the account and saw the OST file increase accordingly.

    I moved those large emails into the archive.

    After 15 minutes or so the OST was compacted in the background and is now back to it's original size.

    So unless I'm missing something this works as we want it to.  You can have retention policies that maintain relatively small mailboxes and cache sizes while still making use of the remaining account space for archives.