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The company I work for has an old web app that integrates with Exchange (online and on-premises) using ExchangeServiceBinding Proxy Class. The app will soon be retired, but it's still used by some of our customers.

Now with the end of support for basic authentication for Online, this would mean changing the code to use Microsoft Graph and OAuth.

I came across a line in this blog entry: https://developer.microsoft.com/en-us/office/blogs/deferred-end-of-support-date-for-basic-authentication-in-exchange-online/ :

"The best way to avoid such failures in your application is to adopt Modern Authentication. If you are unable to do so, you can work with the customer’s administrators, who will have to make a security decision to downgrade their organization’s security stance, to explicitly enable access to your application."

Like I mentioned before, the app will soon be retired, so we are trying to see if there is any way to bypass changing to Microsoft Graph. From the paragraph above I understand that there could be a way, but I don't know exactly the steps we need to take .

Thank you

Ana Munte SPB
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Like I mentioned before, the app will soon be retired, so we are trying to see if there is any way to bypass changing to Microsoft Graph. From the paragraph above I understand that there could be a way, but I don't know exactly the steps we need to take .

While basic auth is being deprecated EWS is not (eg its still the main API in use in OWA) changing your EWS app to use Modern Authentication using a Library like MSAL is very easy even if you want to cater for basic, Hybrid modern Auth and Modern auth it's only a very minimal change. this may help https://gsexdev.blogspot.com/2020/06/modifying-your-ews-wsdl-proxy-code-for.html

Glen Scales
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  • Hi Glen, thanks for the link. It's a good starting point for me, but unfortunately this is an web app, so I need to use the authorization code flow provided by MSAL(IConfidentialClientApplication). I am guessing it should be possible no matter what authentication provider I choose, so I will try this approach. If you have any examples on EWS Proxy Code integrated with authorization code flow it would be great. – Ana Munte SPB Nov 05 '20 at 15:23
  • Hi Glen, based on what you provided, I was able to find a solution, so I will mark it as the right answer. Thanks a lot! – Ana Munte SPB Nov 09 '20 at 09:33