Have a big ost and after archiving the size did not diminish

I have a sbs 2008 sever with exchange 2007. The one email ost on one of the workstation is 45gb and I tried to archive the old emails.
The archive pst has been created but the the ost is still 45gb and the archive pst is gb. I exported the ost to a pst and the size of the pst is 25gb not 45gb. I have to get ost smaller because the workstations outlook takes verylong to startup.

Please assist to have size reduced of mailbox and ost
Lourens van DykIT Technical ConsultantAsked:
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Guy LidbetterCommented:
Hi there,

If the mailbox is very large, consider running in online mode instead of cached mode, unless you have a reason for the emails to be available offline.

Otherwise,have a look at this article



Delete the OST file and allow outlook to recreate it again. The first time this will take some time, but afterwards it should be OK. Otherwise I'd agree with the above. An OST is only needed if it is a laptop that isn't always online and the user still needs to view his mailbox then. For desktop PC's that are stationary inside a company cached mode shouldn't be used, it just slows things down and needs extra resources.

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