Mail is not triggering using C# code

using (SmtpClient smtp = new SmtpClient())
{
    smtp.Port = configuration.GetValue(Constants.EmailServer + Constants.Port);
    smtp.Host = configuration.GetValue(Constants.EmailServer + Constants.SmtpHost);
    smtp.EnableSsl = true;
    smtp.UseDefaultCredentials = false;

    smtp.Credentials = new NetworkCredential("YourUsername", "YourPassword");

    smtp.DeliveryMethod = SmtpDeliveryMethod.Network;
    await smtp.SendMailAsync(message);
}

Dear @Lokesh, you code is straight to the point but I have found some observation such as the code catches SmtpException but doesn't handle it other than printing an error message. You might want to log or handle exceptions differently, depending on your application's requirements. Also the configuration values (SMTP host, port, username, and password) are properly validated before using them. Invalid or missing configuration values can lead to runtime errors.

using (SmtpClient smtp = new SmtpClient())
{
    smtp.Port = _configuration.GetValue(Constants.EmailServer + Constants.Port);
    smtp.Host = _configuration.GetValue(Constants.EmailServer + Constants.SmtpHost);
    smtp.EnableSsl = true;
    smtp.UseDefaultCredentials = false;

    // Provide your SMTP server username and password
    smtp.Credentials = new NetworkCredential("YourSmtpUsername", "YourSmtpPassword");

    smtp.DeliveryMethod = SmtpDeliveryMethod.Network;
    await smtp.SendMailAsync(message);
}

SMTP client (SmtpClient) is configured with the correct username and password for authentication. You should set the NetworkCredential property on the SmtpClient object to provide the necessary credentials.

The error you're encountering suggests that the SMTP server you're trying to connect to requires authentication, and your code is not providing the necessary credentials.

Here's an example of how you can modify your code to include credentials:

using (SmtpClient smtp = new SmtpClient())
{
    // Assuming these values are set in your appsettings.json
    string smtpHost = _configuration.GetValue(Constants.EmailServer + Constants.SmtpHost);
    int smtpPort = _configuration.GetValue(Constants.EmailServer + Constants.Port);
    string smtpUsername = _configuration.GetValue(Constants.EmailServer + Constants.Username);
    string smtpPassword = _configuration.GetValue(Constants.EmailServer + Constants.Password);

    smtp.Port = smtpPort;
    smtp.Host = smtpHost;
    smtp.EnableSsl = true;
    smtp.UseDefaultCredentials = false;

    // Set the credentials
    smtp.Credentials = new NetworkCredential(smtpUsername, smtpPassword);

    smtp.DeliveryMethod = SmtpDeliveryMethod.Network;

    try
    {
        await smtp.SendMailAsync(message);
        Console.WriteLine("Email sent successfully");
    }
    catch (SmtpException ex)
    {
        Console.WriteLine($"Error sending email: {ex.Message}");
    }
}

Make sure to replace Constants.Username and Constants.Password with the appropriate keys from your appsettings.json file. Also, ensure that the provided credentials are valid for the SMTP server you are trying to connect to.

Ensure that you're providing the correct credentials for the SMTP server. You might need to set the NetworkCredential property for the SMTP client.