Managing Huge ost files

I have an exchange 2010/outlook 2010 environment, and I have a number of users that have multiple mailboxes set up in their Outlook.  Each mailbox often has its inbox with dozens and dozens of subfolders set up.  Sometimes when they add a subfolder the subfolder disappears and I then have to delete their profile and ost and rebuild it, and then it works.   The issue at hand is that some of these ost files are 35-40 Gb in size.  Yes, that is correct.  Many of the emails have pictures and or video clips as attachments, and the mailbox size can grow rapidly.  My concern is the size of these ost files.  Is there a problem having such large ost files?  Is there a way to keep these sizes down?
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Amit KumarCommented:
MS states that OST file can be larger till 50 GB in Outlook 2010 and 2013 and 20 GB in Outlook 2003/2007. But if OST grows more than 2 Gb performance issue may occur.

Still I would recommend please install all new updates of Outlook version, also try to create and delete folders in OWA. If issue is not there then it is very clear Outlook OST large size can be an issue.
aerblichAuthor Commented:
How can I reduce OST sizes?
Lee W, MVPTechnology and Business Process AdvisorCommented:
You can increase the 50 GB PST limit if needed.  Additionally, if you upgrade to Outlook 2013, you can control (somewhat limited - 3, 6, 12, 18, 24 months if memory serves) how much mail is cached in the OST.

You can enable Auto Archive but that just moves it from an OST to PST and the PST ends up that large unless you create multiple PSTs (and the PSTs are not available through OWA).  

At the end of the day, the only way to control this is to educate the user on data management - save the images and delete the email.  And then the user must pay attention to this.  Typically, that is accomplished through force - that is, enforcing a quota so if the user doesn't manage their email, they can't send or later receive.  But this policy often doesn't go over well.

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JohnBusiness Consultant (Owner)Commented:
I have my clients archive their email and keep inboxes to 10GB or less.

I prefer to save Video clips into folders and out of Outlook.

I have been doing this for years (over a decade) and it works well.
Seth SimmonsSr. Systems AdministratorCommented:
in addition to getting attachments out of outlook and in the file system, you can compact the ost within outlook
when you remove large amounts of mail, the size of the ost file on disk doesn't shrink automatically

How to compact PST and OST files to eliminate deleted item space in Outlook
Qlemo"Batchelor", Developer and EE Topic AdvisorCommented:
Instead of having people do the "extract content and delete the mail" manually, there are simple solutions allowing to extract content and replace by a link, which might be better, as they still have the mail to search for ...
If those people don't use the PC on the road, then you don't need OST files. For stationary PC's. just disable cached mode for the OST files not to be created. Even if they are on the road with laptops, you don't really need them if the internet connection they have is good. OST files are only of any use if you aren't connected to the LAN or internet, and still need to view your mailboxes. But you can only view your mailboxes during the time you aren't connected. Sending and receiving mails during that time won't work. So it is likely that even on laptops you don't really need OST's most of the time.
Jeffery HayesSystem Support Technician Commented:
Yikes! It sounds like your letting your end-users control how things are done.

First off if there storing large files, photo's, reports, videos, in email format then your need to change that business practice.

Your best bet would be to create a DFS Share on a sever that is backed up and then set it up so the folks can just use the hyper-link to it.

But if you don't want to go by best practices then turn off cache mode and this will help to reduce the size.

Also if you have sharepoint and they have sync enabled (your see Sharepoint List's in the outlook settings) this will also lead to large OST files.
aerblichAuthor Commented:
If I disable cached mode, how will they be able to rapidly retrieve email from, say, a year ago if they want to find it.  Also, wont that put an incredible burden on my network resources if everytime someone opens outlook, it has to retrieve all that email?
Without cached mode, you are working on the Server. You don't have to download anything to the PC first. The server has already downloaded the data, you are just viewing it, or it might temporarily download the message you are viewing, but not the complete mailbox.
Qlemo"Batchelor", Developer and EE Topic AdvisorCommented:
That's the point: In Online (non-cached) mode Outlook only downloads a list of messages, and only the ones which are displayed. There might be more (short) delays when switching folders and views, but that's it. It is as if OWA would be used.
Searches are performed by the server.

I don't agree with rindi totally though. Cached mode makes sense, as long as the OST file is not getting too big at least, because many actions can be performed without even asking Exchange to do anything.
But if the OST file is very big, processing the local file can slow down Outlook significantly. In particular if almost none of the stored stuff gets used at all (which is more likey with fat cache files), as it's the case here.
aerblichAuthor Commented:
@ Qlemo and Rindi:
My concern is what does this do to network traffic and server resources, if every time someone needs to view an email, it has to pull it from across the network and use the exchange server versus a local copy on the workstation.  Also, how does this impact Outlook speed and performance AND searching and indexing?
Qlemo"Batchelor", Developer and EE Topic AdvisorCommented:
As with every caching it works most effective if you view the same stuff often. If emails are viewed once, then deleted or moved to another folder, and might not get reviewed more than a few times, caching will not really help.
With OST files that big you could even see a performance boost if not using cached mode..
In favt nobody will be able to give you figures about the performance and added load n the server side, you'll have to check yourself by trying out. Loosing the Exchange connection often is a sign of overload (network or Exchange Store), and hence an indication.
In regard of search - that's already answered by me.
aerblichAuthor Commented:
@ Qlemo:
Qlemo, you wrote earlier:

"Instead of having people do the "extract content and delete the mail" manually, there are simple solutions allowing to extract content and replace by a link, which might be better, as they still have the mail to search for ...  "

What kind of solutions were you referring to?  This sounds interesting.
Qlemo"Batchelor", Developer and EE Topic AdvisorCommented: is customizable VBA code. Extendable to apply on receive, for example.

Outlook Attachment Remover at is a free Outlook Add-In allowing for some presets without the need of using VBA code. Stripping is on demand only.

Both approachs need to be installed/integrated in each Outlook client.
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