XTAF dictionaries are available to enable an English client to spell check e.g. in German...
Please consider the post of Daniel Nashed's Blog. I can confirm the troubles on Windows! In a test environment, the installation of the XTAF dictionaries from Notes 9.0.1 did destroyed my Notes 10.0.1 Client.
For MacOS I prefere:
- In the notes.ini add the following key: "SPELL_FORCE_LEGACY=1" (you can find the notes.ini in: "~/Library/Preferences/Notes Preferences")
- Download the dictionaries *.dic and *.aff files, so called Hunspell dictionaries, the same you can use with Open Office.
- Copy the *.dic and *.aff files to: ~/Library/Spelling
- Restart Notes 10