@elearning We have checked that there is no issue in sending Test emails if default language is Traditional Chinese.
Please make sure that you have set proper configuration options on Advanced Parameters > E-mail > EMAIL section.
Refer: https://webkul.chatwhizz.com/share/screenshot/649962a37b4603072b06ca34
Also, if you are using SMTP credentials for email, make sure that you enter the correct values.
If issue still persists, please raise a ticket at https://webkul.uvdesk.com/en/customer/create-ticket/.