[PC Advisor UK:] [...] All versions of Outlook use pst files, but the disk location has changed over the years. Right-click your email account on the left in Outlook and select Data File Properties. Click Advanced to see the filename. Only the pst file is essential, but copy the whole folder to back up Outlook’s settings and preferences too. Just copy it back to restore it, or click File, Open, Open Outlook Data File. Outlook can work with any pst file stored anywhere.
[Howtogeek.com:] Backing up your Outlook data file(s) is as easy as copying your .OST or .PST files over to another hard drive, cloud server, thumb drive, or some other storage medium. You remember how to locate your data files?
Open the Mail control panel and click the “Data Files” button. Click “Open File Location…” and you can then back up your data files.
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After following the instructions above, I arrive at:
However, all Outlook Data Files here are .ost, and NOT .pst. In File > Open & Export > Open Outlook Data File, 'Open Outlook Data File' only works for .pst.
What is wrong here? Where's the folder with all the .pst files?
How can I backup all my Outlook email accounts simultaneously?