Having large mail files in Connected on Demand can cause specific users to consume most or all of the available space allocated to your company.  The following article shows how to reduce your Outlook footprint.

Original Article Source:  https://support.office.com

Change how much mail to keep offline

With a Microsoft Exchange Server account, you can decide how much mail is available when working offline with a slow or no network connection.

1. Click File > Account Settings > Account Settings.

   

2. Select an Exchange account, and then click Change.

   

3. Under Offline Settings, move the slider to the desired amount of time, such as All, 12 months, 6 months, 3 months, or 1 month. Note: If you're using Outlook 2016, you can also select an amount of time as short as 3 days.

   

   For example, if you move the slider to 3 months, only mail from the past three months will be synchronized to your Offline Outlook Data (.ost) file from the Exchange server. Items older than 3 months reside only in your mailbox on the server. You can change this setting at any time.

   Cached Exchange Mode, which downloads a copy of your messages, must be turned on.

By default, Outlook configures Exchange accounts to only synchronize a specific number of months, depending on the size of the disk. The following table shows the default Sync Slider setting for different disk sizes: