I have a windows application for sending emails using Microsoft.Office.Interop.Outlook. (Microsoft.Office.Interop.Outlook –version 15.0.4797.1004).

it was working fine till date. now the user upgraded the MS outlook from 2019 to outlook 2021.
now my application is not working. When we try to send email it shows error “Unable to cast COM object Type Microsoft.Office.Interop.Outlook.ApplicationClass to interface type”. I cannot find updated version of Microsoft.Office.Interop.Outlook dll. Please advise how can we resolve this. Thank you

I stopped working on Dotnet for 3 years and shifted to other technology. but still need to support this application. and not sure what is the updated method to resolve Microsoft.Office.Interop.Outlook issue for MS outook 2021.