Asp.net gsuit failure sending mail

A frustrating issue!

When using ASP.NET to send emails through Google Suite (G Suite), you may encounter issues if the setup is not configured correctly. Here are some common causes of failure:

Invalid credentials: Make sure you have entered the correct Gmail address and password in your ASP.NET application.
Less secure apps: Ensure that Less Secure Apps is enabled in your Google Account settings. This setting allows your ASP.NET application to access your Gmail account.
2-Step Verification: If you have 2-Step Verification enabled, you need to generate an App Password and use it in your ASP.NET application instead of your regular password.
OAuth 2.0: G Suite requires OAuth 2.0 authentication. You need to use a library like Google.Apis.Gmail.v1 to authenticate with Google and send emails.
SMTP settings: Verify that your SMTP settings are correct. You can use the following settings:
- Server: smtp.gmail.com
- Port: 587
- Encryption: TLS
- Username: Your Gmail address
- Password: Your Gmail password or App Password
Firewall or proxy issues: Check if your firewall or proxy settings are blocking the connection to Google's SMTP servers.
G Suite restrictions: G Suite has some restrictions on sending emails. For example, you may not be able to send emails to external domains or to a large number of recipients.

To troubleshoot the issue, you can try the following:

Enable debug logging in your ASP.NET application to see the error messages.
Check the Google API Console for any errors or issues with your OAuth 2.0 authentication.
Verify that your SMTP settings are correct and that you can connect to the SMTP server using a tool like Telnet.
Check the G Suite documentation for any specific requirements or restrictions on sending emails.

Here is an example of how you can send an email using ASP.NET and Google Suite:

using Google.Apis.Gmail.v1;
using Google.Apis.Gmail.v1.Data;
using Google.Apis.Services;

// Create a Gmail service instance
var service = new GmailService(new BaseClientService.Initializer
{
    HttpClientInitializer = new ClientSecrets(new ClientSecrets
    {
        ClientId = "YOUR_CLIENT_ID",
        ClientSecret = "YOUR_CLIENT_SECRET"
    }),
    ApplicationName = "YOUR_APPLICATION_NAME"
});

// Create a new email message
var message = new Message
{
    Raw = "Subject: Test email\r\n" +
          "MIME-Version: 1.0\r\n" +
          "Content-Type: text/plain; charset=UTF-8\r\n" +
          "\r\n" +
          "Hello, world!"
};

// Send the email
service.Users.Messages.Send(message, "me").Execute();

Make sure to replace the placeholders with your actual values.

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Asp.net gsuit failure sending mail