Can't delete a 'read receipt'

HI,
I am not able to permanently delete a read receipt, which causes error message in Outlook.
Please see MFCMAPI error message attached.

Thanks
Enrico

<img width="700" height="350" alt="Image" src="https://github.com/user-attachments/assets/44472f69-cb68-40b4-9fa4-047fe98cf4c5" />