The OST file format is used to store emails and other, similar data, that have been extracted from the Microsoft Outlook program (versions 2005 and onwards) or from a Microsoft Exchange server.
It is similar to a Person Folder, or PST, file but it can support much larger files.
.ost File Extension
Developer:
Microsoft
File category:
What are ost files & how to open them - Microsoft Outlook Inbox Off-line Folder File
File category:
Developer:
Microsoft