Shrink .ost file

Jason Watkins
Jason Watkins used Ask the Experts™

A user reads his e-mail on MS Outlook 2007, via Exchange, running on a local SBS 2003 R2 server. There is a great deal of e-mail involved. The .ost file is 9.4GB ins size, with the .pst file being around 75MB in size. Is there any way to shrink the .ost file without deleting e-mail? Performance issues with Outlook have to be because of the file's great size, which is 33% of the HDD's total used footprint. Thanks
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i think u have to archive your email in order to reduce the size of your current OST file.
Shreedhar EtteTechnical Manager
Top Expert 2010
Most Valuable Expert 2011
Top Expert 2011
Should be able to delete the OST, and let it rebuild. Its just the offline copy......

All the emails are safely on the Exchange Server in the mbx..... To be safe, just rename it to outlook.old, and relaunch Outlook....
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Jason WatkinsIT Project Leader


Thanks for the great suggestions. I'll check these out.
How to compact PST and OST files to eliminate deleted item space in Outlook

How to configure the size limit for both (.pst) and (.ost) files in Outlook 2010, Outlook 2007, and in Outlook 2003

How to use offline folders (.ost) file in Outlook 2002
See the "Offline Folders" section which says:
"... the .ost file starts as a mirror image of your folders on the Exchange Server, and works in conjunction with the Exchange Serve during synchronization."

So, as johnb6767 noted, you could delete the .ost file and have it get rebuilt.  It's strange, however, that Exchange synchronization wouldn't keep the .ost file a size that reflects what is currently in your Exchange mailbox, so you might still get stuck with having to do the compaction on the .ost file mentioned in the other articles above.

You mentioned some performance problems and the following article might help:

You may experience performance problems when you are working with items in a large .pst file or in a large .ost file in Outlook 2007
Most Valuable Expert 2011
Top Expert 2011

Remember, it is always goint to be bigger than the mailbox, which is normal....

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