Exchange 2003 - Downside of having mailboxes larger than 2 GB

Posted on 2009-05-01
Last Modified: 2012-06-27
I know that in Exchange 2003, any mailbox larger than 2 GB cannot be exported using ExMerge -- unless you use some filter like date-range.  Are there any other complications/downside of having these huge mailboxes?

(We have to make a case with management because some users simply won't trim their messages. They know they can export to a PST of any size, using Outlook locally.) Thanks.

Question by:nkulsh
    LVL 58

    Assisted Solution


    There is no issue with users having 2GB mailboxes or greater. I know of Exchange deployments were 10GB mailboxes are not unusual. The crucial part is to ensure Exchange is not being used as a file server, but rather as a collaboration protocol; you can often reduce mailbox storage drastically by having users move large attachments from their mailbox and over to a file server, which is a more appropriate form of storage.

    Storage in PST files is a big no-no in an enterprise environment. The overheads, problems with very easy corruption and lack of support for PSTs over a network makes them particularly nasty. You'd want to look at a product such as Symantec Enterprise Vault or GFI MailArchiver for proper archival of older email.

    LVL 13

    Accepted Solution

    First, it's not the size of the mailbox that impacts performance - it is the number of items in the folder or folders that are being accessed on the server.  In particular, performance is largely influenced by the number of items in the most commonly used folders: Calendar, Contacts, Inbox, and Sent Item folder.  

    Having a large number of items in a folder will mean than operations in that folder will take longer.  Operations that depend on the number of items in the folder include adding a new column to the view, sorting on a new column, finds and searches.   Many Outlook plug-ins do sorts or searches as they are running, and these requests may overlap with other Outlook MAPI requests, resulting in a poor user experience.
    If you are running in Cached-Mode, (the default mode for Outlook 2003), then client performance can be an issue.  One thing you should do is keep your OST files (the local data cache) free of fragments.  There is a nice little tool called CONTIG on for this purpose (  

    Check out this article:
    LVL 1

    Author Closing Comment

    Gave extra points to Marine7275 since he also provided a link to a great article.

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