(Go) Office365 SMTP Send Email Client Credentials

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Demonstrates how to send email using the Office365 SMTP server with OAuth2 client credentials. This example uses a new feature available starting in Chilkat v9.5.0.97, which is to provide the client ID, client secret, and tenant ID to Chilkat, and internally Chilkat will fetch OAuth2 access token via client credentials as necessary. Therefore, it is no longer necessary for the application to explicitly fetch the OAuth2 access token beforehand.

Note: This requires the Azure Entra ID application to be configured for client credentials as detailed in this guide: Office365 App Setup for SMTP, POP, IMAP OAuth2 Client Credentials

Note: This example requires Chilkat v9.5.0.97 or greater.

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

    mailman := chilkat.NewMailMan()
    var success bool

    mailman.SetSmtpHost("smtp.office365.com")
    mailman.SetSmtpPort(587)
    mailman.SetStartTLS(true)

    // ----------------------------------------------------------------------------------------
    // Important:
    // Your Azure Entra ID app must be explicitly setup to allow for the OAuth2 client credentials flow.
    // Please follow the detailed guide for how to do it here:
    // Office365 App Setup for SMTP, POP, IMAP OAuth2 Client Credentials
    // 
    // Note: Your registered App must have the SMTP.SendAsApp permission.
    // ----------------------------------------------------------------------------------------

    json := chilkat.NewJsonObject()

    // Use your App's actual client ID here:
    json.UpdateString("client_id","2871da2c-8176-4b7f-869b-2311aa82e743")

    // Use your App's actual client secret here:
    json.UpdateString("client_secret","2hu9Q~r5QuryUcEkNbg1btLtnfU1VUXzhSCG6brH")

    // Use this specific scope.
    json.UpdateString("scope","https://outlook.office365.com/.default")

    // Replace the tenant ID part of the URL with your tenant ID.
    json.UpdateString("token_endpoint","https://login.microsoftonline.com/114d7ed6-71bf-4dbe-a866-748364121bf2/oauth2/v2.0/token")

    // Here is where we use a new feature introduced in Chilkat v9.5.0.97
    // Instead of providing a previously fetched OAuth2 access token, we instead provide the information (above)
    // required for Chilkat to automatically fetch the access token via client credentials.
    mailman.SetOAuth2AccessToken(json.Emit())

    // Use your Office365 email address for the SmtpUsername.
    mailman.SetSmtpUsername("OFFICE365_EMAIL_ADDRESS")

    // Create a new email object
    email := chilkat.NewEmail()

    email.SetSubject("This is a test")
    email.SetBody("This is a test")
    email.SetFrom("MY_NAME <OFFICE365_EMAIL_ADDRESS>")
    email.AddTo("John Doe","somebody@example.com")

    // Call SendEmail to connect to the SMTP server and send.
    // The connection (i.e. session) to the SMTP server remains
    // open so that subsequent SendEmail calls may use the
    // same connection.  
    success = mailman.SendEmail(email)
    if success != true {
        fmt.Println(mailman.LastErrorText())
        mailman.DisposeMailMan()
        json.DisposeJsonObject()
        email.DisposeEmail()
        return
    }

    success = mailman.CloseSmtpConnection()
    if success != true {
        fmt.Println("Connection to SMTP server not closed cleanly.")
    }

    fmt.Println("Mail Sent!")

    mailman.DisposeMailMan()
    json.DisposeJsonObject()
    email.DisposeEmail()