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exchange, OST FILE SIZE, outlook

we have mailboxes with cacahe mode , we save the ost files.

lately i am seeing for some users ost files are like 28 gb but when i check the users mailbox statistics

i see it is 20 gb, so is there any way i can correct this

1) will redoing the outlook profile correct this but this will disrupt the users

2) can i delete the ost file or rename as old ost

i want to do with minimal impact to user.

or is there any script i can run.

we have mailboxes in office 365 and there is no on premise exchange server

can you outline steps , i need to go for.

Vasil Michev (MVP)

The size of the mailbox and the OST size can differ for many reasons, including but not limited to:

- different methods of reporting the size used by the server and the client
- the "cache slider" setting or other filtering settings limiting the amount of data synced
- any additional mailboxes and/or calendars added to the profile
- defragmented/uncompacted OST file

Unless the user is complaining about issues with general slowness or similar in Outlook, the size difference shouldnt bother you. You can remove/recreate the OST or the profile, but there is no way to do this without the end user noticing. If you insist on doing it, you can schedule it over the weekend and you can leave Outlook running so it has enough time to resync the data.

There's detailed info here: https://www.msoutlook.info/question/ost-content-and-size-explained

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timgreen7077

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pramod1

ASKER

So how can I delete ost

We are doing this to correct space issue

timgreen7077

To delete the ost you can do the following, but since you are in cache mode the ost file will just be recreated. You don't want to be deleting ost files to free up space. The ost files are local to the computers so space should be locally used and centrally.

1. Quit Outlook (If it is Running).
2. Go to Run window or press Windows key + r.
3. Type “%LOCALAPPDATA%\Microsoft\Outlook\” in the Run window and click OK. ...
4. Select the .ost (outlook data file) file and either right-click on it and then hit on Delete option or press Delete Key.

Note, once you delete this file and open outlook, it will start rebuilding and I would suggest letting the user know to allow it to finish so that outlook performance will not be affected. It will show all the folders syncing again so allow the sync to finish before working in outlook.

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Vasil Michev (MVP)

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pramod1

ASKER

can u explain cache slider settings, where to do that

timgreen7077

To view what cache is set to do the following:

control panel > mail (32-bit) > email accounts > click email tab > click change

There you will see what you have set for cache in regards to how many months to cache

pramod1

ASKER

Ok while rebuilding my outlook as I deleted ost file I see header counts along with item counts what does that mean

pramod1

ASKER

At bottom

timgreen7077

not sure what you are referring to header counts along with item counts.

pramod1

ASKER

I chose another user whose ost file size was 10 go and mailbox size shown in office 365 was around 1 gb I deleted the ost file and email started downloading again but this user doesn’t have any shared mailbox es in his outlook

How come ost is still showing the same size or around near to 10 go still

timgreen7077

review my response to you about this from the earlier link I sent you to this question.

pramod1

ASKER

Last I saw it was 5gb when downloading emails I will check again tomorrow morning whether it touched back to 10 go or bit less now

Any idea why new ost still shows 6gb where his mailbox size still shows around 1 gab I hope get mailbox command includes all sub folders also in the outlook