Here is a good link that explains the file format in detail.
It explains what company developed the file format,
its uses and what programs can work with this file format.
Once open in one of the programs listed you may be able to
save it in another format.
There are often additional programs and applications as well
but this is a starting point to try.
There are a few that don’t require Office in this list.
If you have further questions let us know.
have to need to convert PST file to MBOX file format. You can try this software PST to MBOX Converter Tool. It is easy to migrate PST file to MBOX
format. This tool supported MS Outlook 2002, 2003, 2007, 2010, 2013, 2016 and