Which Outlook file type is typically used to store archived emails offline?

• A. Outlook bak
• B. Outlook ost
• C. Outlook NK2
• D. Outlook pst

Answer: (D)

Archiving emails offline in Outlook is done with a PST file. A PST, or Personal Storage Table, is a local data file that Outlook uses to store mailbox data—emails, attachments, calendars, contacts—on the computer. This makes it ideal for archiving because you can move older messages into a separate PST, keep it offline, and transport or back it up easily.

In contrast, OST files are offline copies of server mailboxes used to work with Exchange/Office 365 data while disconnected, but they are intended to synchronize with the server rather than serve as a long-term archival store. NK2 is a nickname cache for auto-complete addresses, not email content, and BAK is simply a backup copy with a generic backup extension, not the standard archival format. So PST is the file type typically used to store archived emails offline.