This is a sample console application written in .Net Core that demonstrates how to obtain an OAuth token for logging on to a mailbox using POP. Note that POP is a public protocol and as such it is up to the developer to correctly implement it in their code. The example here is basic, and only intended to show how OAuth fits in to the log-in process. You do not have to use MSAL to obtain the token, but it is a very simple way to do so.

You must register the application in Azure AD as per this guide. You must add a redirect URL of http://localhost (that requirement is specific to this example, as it is what it uses as a redirect URL).

Once the application is registered, the application can be run from a command prompt (or PowerShell console). The syntax is:

POPOAuthSample TenantId ApplicationId

If the parameters are valid, you will be prompted to log-in to the mailbox using the default system browser (POP only supports delegate access). Once done, the application will use the token to log on to the mailbox and get a list of messages. The POP conversation will be shown in the console.

A successful test looks like this: