When importing .PST files from Outlook - in my case MS Outlook 2010 - the import may fail with the following message:
" Error when preparing import: Object reference not set to an instance of an object".
This error can also occur if you attempt to import a whole account from MS Outlook including settings.
The solution that worked for me (using MS Outlook 2010) was to use Outlook’s export functionality (via File > Open > Import > Export to a file > Outlook Data File (.pst)) to export the .PST file to a local folder prior to importing, making sure to use a blank password - this results in a copy of the .PST that appears to be free of whatever causes the error. You should then be able to successfully import that .PST file into emClient.
Note that turning off my Anti-virus software (AVG) and disabling the .PST password in Outlook made no difference i.e. these don’t appear to be a solution to this problem. Regardless, I don’t know if emClient will handle .PST files with passwords.