Thank you for reaching out to us. Regarding the email notification issue you are experiencing, we kindly recommend to downgrade Notification Center to version 1.9.2.3163.
You may obtain the necessary installation packages via the following links:
For other NAS models, please visit the QNAP Download Center to find the corresponding version for your specific model: https://www.qnap.com/go/download
Should you encounter any difficulties during this process or require further assistance, please feel free to open a Support Ticket through our Service Portal. Our technical support team is always here to assist you: https://service.qnap.com/
We appreciate your continued support of QNAP products.