disabled cached mode, but Outlook still using OST

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Outlook version
Email Account
Exchange Server

I have a site which uses Outlook 2003 in cached mode, this was enforced via Group Policy. Due to issues with large OSTs I wish to revert back to non-cached.

I have changed the GPO to disable cached mode, but the effect is not what we desire.

Although the two cached settings within the mail profile are no longer ticked, Outlook is still referencing the OST file when running. From Googling this, it appears Outlook continues to cache the calendar (and possibly contacts). This is confirmed if I close Outlook, delete the OST file, then start Outlook. It creates a new smaller OST files (containing presumably just the Calendar).

I really need to stop Outlook connecting to the existing OST as they are huge and easily corruptible. We frequently get errors about 'Outlook did not close down properly and is checking files for errors'.

So, the only way I have found to get around this is to create a new mail profile from scratch and add the registry key NoOST (taken from http://support.microsoft.com/kb/276248). This forces Outlook to not create an OST at startup.

However, this isn't practical as the user loses any Outlook settings, and more importantly they loose their autocomplete for nicknames (.NK2).

I guess doing all of the above is scriptable? Any other help or suggestions to disable cache and stopping Outlook create a new OST on the existing mail profile?



Senior Member
Outlook version
Outlook 2010 64 bit
Email Account
Exchange Server
Did you remove cached mode in the profile itself? From memory - tools, account settings - double click on the account then more settings. Find the option to not use cached mode and also disable the ost.

This screenshot is from Outlook 2010, but I recall the disalog didn't change much over the years.



Senior Member
Outlook version
Outlook 2010 64 bit
Email Account
Exchange Server
BTW, I'm not sure if this is scriptable - but one solution might be to remove the account and replace it (possibly using a PRF) - the profile is not touched, so the NK2 and other customizations remain.
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