Issue:
Problems with Outlook crashing which due to mailboxes growing to the point where their OST was about 85GB and continuing to increase.
Summary:
With email being one of the primary means of sending files in today’s business environments and file types getting larger and larger, some organizations are suffering from a) performance issues with Outlook OST files growing too large and/or b) their OST limit default being 50GBs for all current version of Outlook.
Our customers primarily use Office 365 for Business.
Solution & Links:
One way of Managing Group Policies is through Active Directory Group Policy Objects.
We had a client who was having problems with their Outlook crashing which we found was due to one of their mailboxes growing to the point where their OST was about 85GB and continuing to increase. This was a problem because Outlook will sometimes have performance issues or stop functioning properly after the OST file grows larger than 50GB. This started occurring on many workstations so we had to put in a solution that would be automated for any user.
In order to correct this problem, we implemented two Group Policies. The first allowed the OST file to grow to 100GB (the normal default registry limit is 50GBs) – in the past we would manually run .reg files to add the needed registry entries for a 100GB or 150GB OST limit. The second set the default time period for the Offline Cache to 3 months rather than the normal default of 1 year – and it would prevent users from changing it as the Group Policy would kick in if changed and bring it back to 3 months . After testing this, these GPOs were applied to the entire organization.
Depending on your needs, you can set the cache limit to whatever works for your organization.
These are the steps that were taken to do this:
EMAIL CACHE LIMIT IN MANAGING GROUP POLICY:
- Open Group Policy Management
- Create a Group Policy Object (GPO) called “EmailMailboxCache3Months”
- Download the Administrative Template files (ADMX/ADML) for Microsoft 365 Apps for enterprise/Office LTSC 2021/Office 2019/Office 2016 and the Office Customization Tool for Office 2016 https://www.microsoft.com/en-us/download/details.aspx?id=49030
- Follow the instructions to extract Outlook administrative template file into the “C:\Windows PolicyDefinitions” folder and the language file into the “C:\Windows\Policy Definitions\en-us”
https://www.alitajran.com/install-administrative-template-files-for-microsoft-office/
- Edit the GPO “EmailMailboxCache3Months” and set “Cached Exchange Mode Sync Settings” to 3 Months
SET A NEW MAXIMUM ON THE PST/OST SIZE LIMIT IN OUTLOOK:
This setting essentially overrides the 50GB default Outlook limit and sets it to what you configure it to be.
- Create GPO called “EmailOSTSetMax100GB”
- Locate the setting for Max Outlook Data File Size (“Large PST: Absolute Maximum Size”) and set as 100 GB max size in the “EmailOSTSetMax100GB” GPO
- In Group Policy Management, right click on the organization unit domain folder that you want to apply these GPOs to, click “Link an Existing GPO…” and select the “EmailOSTSetMax100GB” and “EmailMailboxCache3Months” GPOs
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