SysInfo PST File Viewer - Outlook PST File Viewer Tool enable users to open, view or read PST files without requiring Outlook, it scans all the important items of PST such as calendars, contacts, notes, tasks and journal entries etc.
Okular - Okular is a universal document viewer based developed by KDE.
Coolutils Outlook Viewer - Coolutils Outlook Viewer is an all-in-one open application that lets you open and views PST or OST files, and you do not need to install Outlook on your computer.
Sumatra PDF - Sumatra PDF is a slim PDF/DjVu/EPUB/XPS/CHM/CBR/CBZ/MOBI viewer for Windows.
SysTools PST Viewer - PST Viewer Freeware tool to open, read & view PST files without Outlook 2019, 2016, 2013, 2010, 2007.
Foxit Reader - Foxit Reader is a free and light-weight multi-platform PDF document viewer.