(Go) 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.

Chilkat Go Downloads Go Package for Windows, MacOS, Linux, Alpine Linux, Solaris

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

    mailman := chilkat.NewMailMan()

    mailman.SetMailHost("outlook.office365.com")
    mailman.SetMailPort(995)
    mailman.SetPopSsl(true)

    // Use your O365 email address here.
    mailman.SetPopUsername("OFFICE365_EMAIL_ADDRESS")

    // When using OAuth2 authentication, leave the password empty.
    mailman.SetPopPassword("")

    // Load our previously obtained OAuth2 access token.
    jsonToken := chilkat.NewJsonObject()
    success := jsonToken.LoadFile("qa_data/tokens/office365.json")
    if success == false {
        fmt.Println(jsonToken.LastErrorText())
        mailman.DisposeMailMan()
        jsonToken.DisposeJsonObject()
        return
    }

    mailman.SetOAuth2AccessToken(*jsonToken.StringOf("access_token"))

    // Make the TLS connection to the outlook.office365.com POP3 server.
    success = mailman.Pop3Connect()
    if success != true {
        fmt.Println(mailman.LastErrorText())
        mailman.DisposeMailMan()
        jsonToken.DisposeJsonObject()
        return
    }

    // Authenticate using XOAUTH2
    success = mailman.Pop3Authenticate()
    if success != true {
        // 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 {

            // Refresh the OAuth2 access token, and if successful, save the new (refreshed) access token and try authenticating again.
            oauth2 := chilkat.NewOAuth2()

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

            // Replace these with your Azure App Registration's actual values.
            oauth2.SetClientId("CLIENT_ID")
            oauth2.SetClientSecret("CLIENT_SECRET")

            // Get the "refresh_token"
            oauth2.SetRefreshToken(*jsonToken.StringOf("refresh_token"))

            // Send the HTTP POST to refresh the access token..
            success = oauth2.RefreshAccessToken()
            if success != true {
                fmt.Println(oauth2.LastErrorText())
                mailman.DisposeMailMan()
                jsonToken.DisposeJsonObject()
                oauth2.DisposeOAuth2()
                return
            }

            fmt.Println("New access token: ", oauth2.AccessToken())
            fmt.Println("New refresh token: ", oauth2.RefreshToken())

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

            // Save the new JSON access token response to a file.
            sbJson := chilkat.NewStringBuilder()
            jsonToken.SetEmitCompact(false)
            jsonToken.EmitSb(sbJson)
            sbJson.WriteFile("qa_data/tokens/office365.json","utf-8",false)

            fmt.Println("New Access Token = ", oauth2.AccessToken())

            // Update the mailman with the new access token.
            mailman.SetOAuth2AccessToken(oauth2.AccessToken())

            // Retry the authentication.
            success = mailman.Pop3Authenticate()
            if success == false {
                fmt.Println(mailman.LastErrorText())
                mailman.DisposeMailMan()
                jsonToken.DisposeJsonObject()
                oauth2.DisposeOAuth2()
                sbJson.DisposeStringBuilder()
                return
            }

        }
        else {
            fmt.Println(mailman.LastErrorText())
            mailman.DisposeMailMan()
            jsonToken.DisposeJsonObject()
            oauth2.DisposeOAuth2()
            sbJson.DisposeStringBuilder()
            return
        }

    }

    // Find out how many emails are on the server..
    numEmails := mailman.CheckMail()
    if numEmails < 0 {
        fmt.Println(mailman.LastErrorText())
        mailman.DisposeMailMan()
        jsonToken.DisposeJsonObject()
        oauth2.DisposeOAuth2()
        sbJson.DisposeStringBuilder()
        return
    }

    // Examine the POP3 session log:
    fmt.Println(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 {
        fmt.Println(mailman.LastErrorText())
        mailman.DisposeMailMan()
        jsonToken.DisposeJsonObject()
        oauth2.DisposeOAuth2()
        sbJson.DisposeStringBuilder()
        return
    }

    fmt.Println("Finished.")

    mailman.DisposeMailMan()
    jsonToken.DisposeJsonObject()
    oauth2.DisposeOAuth2()
    sbJson.DisposeStringBuilder()