How to download email attachment from Exchange Server

The EWS Managed API provides a simple and full-featured interface for developing and extending applications that use Exchange Web Services (EWS). Whether you are using Visual Studio or another code editor to develop your EWS Managed API application, you will need to make a reference to the EWS Managed API assembly. If you haven't installed the EWS Managed API already, be sure to download the API.

https://docs.microsoft.com/en-us/exchange/client-developer/exchange-web-services/how-to-reference-the-ews-managed-api-assembly

Add required parameters  as per your requirements

You can get the code from here

https://docs.microsoft.com/en-us/exchange/client-developer/exchange-web-services/how-to-get-attachments-by-using-ews-in-exchange

Thanks,
Uma