Some time between Ignition 7.8.3 and Ignition 7.9.5 sending Chinese characters in emails broke, but as of 7.9.5 it’s working again without doing anything special. Here’s an example script that’s working as of 7.9.5:
Something is different with your setup than we use for testing. Could you contact support – that way we can figure out what it is and either help you get it set up correctly or fix a bug we don’t know about. Thanks!
IIRC, email standards don't have a way to use normal content encoding information with subject headers. There's an alternate form that is required.... RFC1342.