This provides a seamless and lag-free user experience.
The changes are later synchronized with the mailbox on the server as soon as the system connects to the internet. It allows user to access their Outlook emails and do certain changes, even when the system is offline. The OST file stores mailbox items, such as emails, contacts, attachments, notes, journals, etc. OST is an Outlook data file created by Outlook when you set up or configure Exchange server account and enable the Offline mode (Cached Exchange Mode).
