Single instance storage is per store (database). You can't really "lose" it. Exchange will never keep more than one copy of a message in the database. i.e. You move a user from store A to store B. He has a message from another user on store B in his inbox. When the mailbox is being moved, exchange checks all messages coming in during the move process and realizes that the message in the inbox on user A, is already in the sent items folder of user B. Therefore, it doesn't store it again, it just puts a pointer to the message. The only time file sizes really grow, is when you move 5 users from store A, all with the same message, to 5 different stores. Then the message has to be copied 5 times to the new stores. Any subsequent users who get moved to those stores with the same message, will get pointers, provided the message still exists. i.e. once the user has emptied his deleted items folder, the message is no longer in the store, so any subsequent moves will copy it in again. Greg ----- Original Message ----- From: Danny To: exchangelist@xxxxxxxxxxxxx Sent: Wednesday, February 21, 2007 3:18 PM Subject: [ExchangeList] Re: 2003 SP2 to 2003 SP2 user mailbox size grew Do you happen to have any Microsoft documentation that confirms this? I found this KB, which stirs up more questions: http://support.microsoft.com/kb/175481 Thanks, ...D On 2/20/07, Periyasamy, Raj <Raj.Periyasamy@xxxxxxxxxxxx> wrote: The moment you move your mailbox from one store to another, you lose the SSI, not just Exmerge. Regards, R From: exchangelist-bounce@xxxxxxxxxxxxx [mailto:exchangelist-bounce@xxxxxxxxxxxxx] On Behalf Of Danny Sent: Monday, February 19, 2007 11:59 AM To: exchangelist@xxxxxxxxxxxxx Subject: [ExchangeList] Re: 2003 SP2 to 2003 SP2 user mailbox size grew No Exmerg'ing going on here - I am aware of the single instance storage loss. 2003 SP2 to 2003 SP2, same org, same domain. Exchange System Manager -> Mailbox Store -> Exchange Tasks -> Move Mailbox. Thanks, ...D On 2/19/07, Exchange Mailing List <ExchangeMailingList@xxxxxxxxxx> wrote: Depends how you did it. If you exmerged, then you have lost single instance storage. S From: exchangelist-bounce@xxxxxxxxxxxxx [mailto: exchangelist-bounce@xxxxxxxxxxxxx] On Behalf Of Danny Sent: Monday, February 19, 2007 12:23 PM To: exchangelist@xxxxxxxxxxxxx Subject: [ExchangeList] 2003 SP2 to 2003 SP2 user mailbox size grew Moved mailboxes to a new server. Confirming this is normal and by how much should they grow? Thanks, ...D -- CPDE - Certified Petroleum Distribution Engineer CCBC - Certified Canadian Beer Consumer -- CPDE - Certified Petroleum Distribution Engineer CCBC - Certified Canadian Beer Consumer