If you're using an Exchange email account, you can delete the offline Outlook Data File (.ost) and Outlook will recreate the offline Outlook Data File (.ost) the next time you open Outlook.

Outlook Data Files (.ost) are used when you have an Exchange account and want to work offline or use or use the default Cached Exchange Mode. This type of data file is also used for accounts that you …

Outlook Data Files (.pst), or Personal Storage Tables files, contain Outlook user messages and other Outlook items, such as contacts, appointments, tasks, notes, and journal entries. You might also use …

Learn how to find out the size of your mailbox and its folders and how to compact Outlook Data Files (.pst and .ost), which might help improve performance.

Some accounts (IMAP, Microsoft Exchange Server, and Outlook.com) use an offline Outlook Data File (.ost). This is a synchronized copy of the messages saved on a server.

瞭解如何找出信箱及其資料夾的大小，以及如何壓縮 Outlook 資料檔 (.pst 和 .ost) ，這可能有助於改善效能。

當您有 Exchange 帳戶，並且想要離線工作或使用預設 Exchange 快取模式 (離線) 時，就會使用 Outlook 資料檔 (.ost)。 此資料檔類型也適用於您透過適用於 Outlook.com (先前稱為 Hotmail) 的 Outlook …

如果您使用的是 Exchange 電子郵件帳戶，您可以刪除離線 Outlook 數據檔 (.ost) ，Outlook 會在下次開啟 Outlook 時重新建立離線 Outlook 資料檔 (.ost) 。

Export Outlook email, contacts, and calendar to move them to another computer or so that you can make a backup of your information.

Even if your account uses an offline Outlook Data File (.ost) for all of its day-to-day information, you may still have an archive.pst file that contains older information.