1) Make sure that the users have full share permissions to this folder, not just Read rights.
2) Make sure the users are accessing the Server share from their workstations.
3) The addresstranslation.bin file might be corrupt. To resolve this, do the following:
In the NotesDTApp.ini file there is an entry: 'SMTPTranslationTable=\\servername\C$\SSDM\addresstranslation.tsv'. Locate this file and rename it
rerun a 'directory export' and try again - this will create a new addresstranslation.bin file.
4) Finally, navigate to 'C:\Program Files\Quest Software\Quest Notes Migrator for Exchange\ToolsCache', which is a hidden folder and try running this copy of the SSDM tool.