OST Viewer - Version 4.0 How to open OST file without Exchange Server? We provide a freeware OST Viewer tool lets you to read & view OST file easily without connecting to MS Exchange Server. Administrators frequently face the heat of the situation when they have to look out for some important data in OST file. Resolving this issue, we offer you free OST Viewer software that allows you to open ost file & view the content & attachment of OST file without the requirement of any connection with MS Exchange Server. This software lets the user scan corrupt OST file and displays the data saved in it including email messages, contacts, calendars, notes etc in a proper folder structure. You can download a freeware version of software, lets you can read & view all email data of OST file.