C# starttls is required to send mail

A great topic!

In C#, when sending emails using the System.Net.Mail namespace, you may encounter situations where the SMTP server requires STARTTLS (Transport Layer Security) encryption to be enabled before sending the email. This is a common requirement for many email providers, including Gmail, Outlook, and others.

To enable STARTTLS in C#, you can use the SmtpClient class and set the EnableSsl property to true. Additionally, you need to specify the SmtpServer property with the SMTP server's hostname or IP address.

Here's an example:

using System.Net.Mail;

// Create a new SmtpClient instance
SmtpClient client = new SmtpClient();

// Set the SMTP server and port
client.Host = "smtp.gmail.com";
client.Port = 587;

// Enable SSL/TLS encryption
client.EnableSsl = true;

// Set the email sender and recipient
MailMessage message = new MailMessage("[email protected]", "[email protected]", "Subject", "Body");

// Send the email
client.Send(message);

In this example, we're using the smtp.gmail.com SMTP server, which requires STARTTLS encryption. By setting EnableSsl to true, we're telling the SmtpClient to establish a secure connection with the SMTP server using TLS.

If you're using a different SMTP server that requires STARTTLS, you'll need to adjust the Host and Port properties accordingly.

Note that some SMTP servers may also require authentication using a username and password. You can set these using the Credentials property:

client.Credentials = new NetworkCredential("username", "password");

Remember to replace username and password with your actual SMTP credentials.