Outlook gal not updating in cached mode
Don’t fear the OST; instead, embrace full disk encryption such as that offered by Bit Locker or various third party vendors, and ensure strong authentication is required to gain local access to the disk.
It’s far better to secure all the data, then to shoot yourself in the foot with regards to Outlook performance.
For Office 365 or other hosted Exchange customers, the answer is easy – use cached mode.
The Exchange CAS server is not local to you, so you will have higher latency and cached mode will accommodate this.
Cached mode needs local storage and that’s a problem for tablets with small SSDs or VDI systems without persistent storage.
Running in cached mode, the Outlook client looks to the local OST file for all access, including reads and searches, while a separate process checks for new mail on the server and syncs data to the local cache.You should use cached mode anytime a user must access their mail without network connectivity, such as users who travel.