To convert OST to PST, the objective is to transfer all mailbox information, including emails, contacts, calendars, and attachments, from the offline Outlook file into a portable PST format. OST files are also associated with one profile and server of Outlook, which creates most cases of inaccessibility. By changing from OST to PST, an individual can safely access, back up, or modify the data in Outlook, preserving the structure of folders, email properties, and other attachments, without relying on the original email account.