OSTOutlook Offline Storage File
OST or Offline Storage Files represent user's mailbox data in offline mode on local machine upon registration with Exchange Server using Microsoft Outlook. It is automatically created on the first use of Microsoft Outlook upon connectivity with server. Once the file is created, the data is synchronized with the email server so that it is available offline as well in case of disconnectivity from email server.
MBOXEmail Mailbox File
MBox file format is a generic term that represents a container for collection of electronic mail messages. The messages are stored inside the container along with their attachments. Messages from an entire folder are saved in a single database file and new messages are appended to the end of the file. Numerous applications and API provide support for MBox file format such as Apple Mail and Mozilla Thunderbird.