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I've got an issue with a user whose Outlook runs really slow. Her Exchange mailbox is ~4.6 Gb, which while large should be alright (she's got a 3.2 GHz i5 with 4 Gb RAM)? However, the .ost-file is 20.2 Gb. Why is it so much larger? I've run scanpst/scanost, which reported it repaired a few errors, but the size didn't shrink.

I've turned off Cached mode since it was causing thousands of conflict-copies, which was also filling up this user's mailbox.

Any suggestions on what to do? We're running Outlook 2007 on Windows 7, connected to Exchange 2003 on SBS 2003.

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up vote 6 down vote accepted

The OST will not shrink by moving the files. You will need to compact them. Right-click on the OST, Properties, Advanced, Compact Now.

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+1. Or, if she's got a couple of hours, simply delete (or rename) the ost and let it re-sync from the server. – SmallClanger Mar 22 '11 at 11:15

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