When you use Microsoft Outlook in cached mode, what I always recommend, and you add additional mailboxes to your outlook profile, you will notice that the OST file will grow. Outlook will download the mailbox items (mails, calendar entries, contacts etc.), and store them in the OST file. This is the default behaviour since Microsoft Outlook 2010. If you want to disable this behaviour, you have two options:
- Edit the registry
- Use a group policy object (GPO)
Edit the Windows registry
The easiest way is to use a reg file. Copy this text into a file and save it as disablecachedmode.reg. Then double click the file and confirm, that you want to import the registry file.