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Q175706: XADM: How Moving Mailboxes Affects Single Instance Storage

Article: Q175706
Product(s): Microsoft Exchange
Version(s): 4.0,5.0,5.5
Operating System(s): 
Keyword(s): 
Last Modified: 12-FEB-2002

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The information in this article applies to:

- Microsoft Exchange 2000 Server 
- Microsoft Exchange Server, versions 4.0, 5.0, 5.5 
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SUMMARY
=======

Exchange Server maintains single-instance storage of messages even when users
are moved between servers in a site.

For example, assume the following configuration:

  Server 1: Users A, B, and C
  Server 2: User D

When User A sends the same message to users B, C, and D, Exchange Server will
make a single instance of the message on server 1 for all three users, since A,
B, and C are on the same server. Even the message in the Sent Items folder of
the sender (user A) is a single instance of the messages in the Inboxes of users
B and C. Because User D is on a different server, Exchange Server will send a
message to server 2, which will be stored on that server.

Now assume that user B is moved to server 2. Exchange Server will create a single
instance of the message for B off of the copy of the message that user D has,
provided that user D has not deleted the message. If user D has already deleted
the message, then Exchange Server will create a single instance of the message
off the copy in D's Deleted Items folder. If user D also deleted the message
copy in the Deleted Items folder, then Exchange Server creates a new message and
sends it to server 2.

The same process will take place if users B and C are moved to server 2. Exchange
Server will maintain a single instance of the message for users B and C, based
on the message in the Inbox of user D. If user D has already deleted the
message, Exchange Server will attempt to use the copy in user D's Deleted Items
folder. If user D has already emptied the Deleted Items folder, then Exchange
Server will create a new message and send it to server 2.

Additional query words: single instance

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Keywords          :  
Technology        : kbExchangeSearch kbExchange500 kbExchange550 kbExchange400 kbZNotKeyword2
Version           : :4.0,5.0,5.5
Issue type        : kbinfo

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