Running Outlook in Cache model or not

 I have SBS2011/Exchange Server 2010 and Outlook 2013.
 I have been enabling Cache mode whenever I set up Outlook on user computers for safety just in case Exchange Server (20 mailbox database > 200GB in size) crashes  or not available for extended period of time.
 The downside of that is, from time to time, local copy file gets corrupted as some user mailbox size exceeds 20GB. (I know max size for OST is 50GB) Sometimes it takes a long time to open Outlook (maybe because Outlook has to sync its local contents against Exchange Server before opening Outlook?).
 Whenever the problem occurs, I simply delete existing OST file and re-open Outlook so that new OST is created. The inconvenience is that users complain that they can't perform search until indexing to complete.

When you perform a search in Outlook, does it make a difference whether Outlook is running in Cache mode or not?
 I just like to get know how other experts are managing Outlook data.
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Ibrahim BennaTechnology LeadCommented:
When you are running Outlook in cached mode, all searches are performed locally on the OST file as opposed to when you are running in Online mode and all searches are done on the exchange server. Having your Outlook running in online mode would mean all your users would be connecting to exchange to retrieve an email and all searches will be performed by the exchange server. Having a beefy server you will not notice much of a difference but if the server is under-resourced then you will see an impact. - read this to better understand Outlook and searching.

I always recommend to my clients to use Outlook in cached mode as it definitely improves performance for the end-users. If the OST file is getting corrupted consistently, you may have other issues (maybe your antivirus is scanning the file). You may want to consider excluding OST from being scanned by antivirus (

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I would definitely recommend running in cached mode, this allows the users to reference the local copy for any searches as opposed to the online option, where your users will be struggling for bandwidth to get search results. if you have mobile computers in use, this also allows the users to be offline and reference emails locally. it just eases the email access experience for the end user.
sgleeAuthor Commented:
Since 50GB is limit on OST file, how do you handle those mailboxes beyond the limit?
Do you archive some and backup those archive PST files from local HD to the network/file server?
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Ibrahim BennaTechnology LeadCommented:
For larger mailboxes like that I recommend using exchange archive mailboxes so most of the historic data will be on a different secondary mailbox for each user. searching on outlook will automatically be done on both mailboxes but only the primary mailbox containing the latest data will be cached.
sgleeAuthor Commented:
"I recommend using exchange archive mailboxes" --> can you be more specific?
Are you talking about creating another mailbox for those users with mailbox size over 50GB?
For example, if the main mailbox name is "John Doe", another mailbox name would be "John Doe Archive" and set it up so that "John Doe" can access "John Doe Archive" account in Outlook?
Ibrahim BennaTechnology LeadCommented:
exchange 2010 introduced archive mailboxes that basically replace using pst files. they are online mailboxes created for existing mailboxes and it automatically creates a second mailbox for the user on exchange. it is associated automatically to the user so you don't have to worry about permissions and such.
sgleeAuthor Commented:
I have not had time to try "exchange 2010 introduced archive mailboxes that basically replace using pst files", but I will try your suggestion in coming days and post results.
sgleeAuthor Commented:
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