Which file extensions are used for Outlook Express mailbox storage?

• A. Mbx or Dbx extensions
• B. Pst extensions
• C. Ost extensions
• D. Eml extensions

Answer: (A)

Outlook Express stores messages in mailbox files on disk, with each folder having its own mailbox file. The typical container for these mailboxes is the DBX format, so you’ll see files like Inbox.dbx, Sent Items.dbx, and so on. In older versions, mailbox files could also use the MBX extension, which is why both MBX and DBX appear as possible formats for Outlook Express storage. This is distinct from PST or OST files used by other Microsoft mail clients, or from EML files, which represent individual messages rather than whole mailbox stores. So, the best answer reflects that mailbox storage uses MBX or DBX extensions.