I am not aware of any fee email client that can support pst files directly, but I believe in Mozilla Thunderbird, a free email program, a PST file can be imported after a file format conversion. Thunderbird supports MBOX file format. When a PST file is converted into MBOX then it can be imported into Thunderbird. However I think that you need a 3rd party converter such as Stellar PST to MBOX Converter. However this is not free.
Of course there maybe other conversion apps out there that are free.
You can also get a converter for .msg files which as I mention you can drag out individual or multiple messages from Outlook. Again it's not a free converter.
It's not something I use myself so that's about all I can offer.
Edited by rogerfp (Thu 26-Mar-15 22:02:12)