ost file starts as a mirror image of your folders on the server running Exchange.

Offline folders are stored in your Offline Folder file (.ost), which is different from a Personal Folders file (.pst). The next time that you establish a connection to the server running Exchange, the offline folders are synchronized. Offline folders make it possible to work with the contents of an Exchange folder while you are offline, that is, not connected to the network. Use offline folders with your Exchange account If you're running in a virtual desktop environment, we recommend you only synchronize one month of data. If you're using Outlook with an Microsoft 365 account, we recommend you use Cached Exchange Mode.īy default, Outlook configures Exchange and Microsoft 365 accounts to only synchronize 12 months of your email.Ĭhanging the amount of data to synchronize can affect the time it takes Outlook to open as well as the amount of storage space Outlook uses on your computer. You can change this setting at any time.Ĭached Exchange Mode, which downloads a copy of your messages, must be turned on. Items older than 3 months reside only in your mailbox on the server. Note: If you're using Outlook 2016, you can also select an amount of time as short as 3 days.įor 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. Under Offline Settings, move the slider to the desired amount of time, such as All, 12 months, 6 months, 3 months, or 1 month.

Select an Exchange or Microsoft 365 account, and then click Change. Change how much mail to keep offlineĬlick File > Account Settings > Account Settings. Working Offline on the status bar also goes away when you’re working online.

The button text doesn’t change, but it’s only highlighted when you’re working offline. When you’re ready to work online again, click Send / Receive > Work Offline. You know you’re working offline when Work Offline is highlighted on the ribbon or Working Offline appears on the status bar at the bottom of the Outlook window. When Outlook switches between working online and offline, all email accounts are changed. Switch between working offline and working online

Outlook 365 working offline stuck