(Xojo Plugin) POP3 Auto-Refresh Office365 Access Token

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Demonstrates how to automatically recover from an expired OAuth2 access token when OAuth2 authentication fails in the POP3 protocol. If the server responds with "-ERR Authentication failure: unknown user name or bad password.", then we refresh the access token and retry.

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// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

Dim mailman As New Chilkat.MailMan

mailman.MailHost = "outlook.office365.com"
mailman.MailPort = 995
mailman.PopSsl = True

// Use your O365 email address here.
mailman.PopUsername = "OFFICE365_EMAIL_ADDRESS"

// When using OAuth2 authentication, leave the password empty.
mailman.PopPassword = ""

// Load our previously obtained OAuth2 access token.
Dim jsonToken As New Chilkat.JsonObject
Dim success As Boolean
success = jsonToken.LoadFile("qa_data/tokens/office365.json")
If (success = False) Then
    System.DebugLog(jsonToken.LastErrorText)
    Return
End If

mailman.OAuth2AccessToken = jsonToken.StringOf("access_token")

// Make the TLS connection to the outlook.office365.com POP3 server.
success = mailman.Pop3Connect()
If (success <> True) Then
    System.DebugLog(mailman.LastErrorText)
    Return
End If

// Authenticate using XOAUTH2
success = mailman.Pop3Authenticate()
If (success <> True) Then
    // If we're still connected to the mail server, then it means the server sent a non-success response,
    // Such as:  -ERR Authentication failure: unknown user name or bad password.
    If (mailman.IsPop3Connected = True) Then

        // Refresh the OAuth2 access token, and if successful, save the new (refreshed) access token and try authenticating again.
        Dim oauth2 As New Chilkat.OAuth2

        // Use your actual Directory (tenant) ID instead of "112d7ed6-71bf-4eba-a866-738364321bfc"
        oauth2.TokenEndpoint = "https://login.microsoftonline.com/112d7ed6-71bf-4eba-a866-738364321bfc/oauth2/v2.0/token"

        // Replace these with your Azure App Registration's actual values.
        oauth2.ClientId = "CLIENT_ID"
        oauth2.ClientSecret = "CLIENT_SECRET"

        // Get the "refresh_token"
        oauth2.RefreshToken = jsonToken.StringOf("refresh_token")

        // Send the HTTP POST to refresh the access token..
        success = oauth2.RefreshAccessToken()
        If (success <> True) Then
            System.DebugLog(oauth2.LastErrorText)
            Return
        End If

        System.DebugLog("New access token: " + oauth2.AccessToken)
        System.DebugLog("New refresh token: " + oauth2.RefreshToken)

        // Update the JSON with the new tokens.
        success = jsonToken.UpdateString("access_token",oauth2.AccessToken)
        success = jsonToken.UpdateString("refresh_token",oauth2.RefreshToken)

        // Save the new JSON access token response to a file.
        Dim sbJson As New Chilkat.StringBuilder
        jsonToken.EmitCompact = False
        success = jsonToken.EmitSb(sbJson)
        success = sbJson.WriteFile("qa_data/tokens/office365.json","utf-8",False)

        System.DebugLog("New Access Token = " + oauth2.AccessToken)

        // Update the mailman with the new access token.
        mailman.OAuth2AccessToken = oauth2.AccessToken

        // Retry the authentication.
        success = mailman.Pop3Authenticate()
        If (success = False) Then
            System.DebugLog(mailman.LastErrorText)
            Return
        End If

    Else
        System.DebugLog(mailman.LastErrorText)
        Return
    End If

End If

// Find out how many emails are on the server..
Dim numEmails As Int32
numEmails = mailman.CheckMail()
If (numEmails < 0) Then
    System.DebugLog(mailman.LastErrorText)
    Return
End If

// Examine the POP3 session log:
System.DebugLog(mailman.Pop3SessionLog)

// The POP3 session log will look something like this:

// **** Connected to outlook.office365.com:995
// < +OK The Microsoft Exchange POP3 service is ready. [QwBIADIAUABSADEANgBDAEEAMAAwADEAMgAuAG4AYQBtAHAAcgBkADEANgAuAHAAcgBvAGQALgBvAHUAdABsAG8AbwBrAC4AYwBvAG0A]
// > AUTH XOAUTH2
// < + 
// > <base64 string in XOAUTH2 format>
// < -ERR Authentication failure: unknown user name or bad password.
// > AUTH XOAUTH2
// < + 
// > <base64 string in XOAUTH2 format>
// < +OK User successfully authenticated.
// > STAT
// < +OK 248 46637086

// End the POP3 session and close the connection to the GMail server.
success = mailman.Pop3EndSession()
If (success <> True) Then
    System.DebugLog(mailman.LastErrorText)
    Return
End If

System.DebugLog("Finished.")