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How can I make SMTP authenticated in C#

Posted by: admin November 29, 2017 Leave a comment


I create new ASP.NET web application that use SMTP to send message. The problem is the smtp was not authenticated from who send the message.

How can I make SMTP authenticated in my program? does C# have a class that have attribute for enter username and password?

using System.Net;
using System.Net.Mail;

SmtpClient smtpClient = new SmtpClient();
NetworkCredential basicCredential = 
    new NetworkCredential("username", "password"); 
MailMessage message = new MailMessage(); 
MailAddress fromAddress = new MailAddress("[email protected]"); 

smtpClient.Host = "mail.mydomain.com";
smtpClient.UseDefaultCredentials = false;
smtpClient.Credentials = basicCredential;

message.From = fromAddress;
message.Subject = "your subject";
//Set IsBodyHtml to true means you can send HTML email.
message.IsBodyHtml = true;
message.Body = "<h1>your message body</h1>";
message.To.Add("[email protected]"); 

catch(Exception ex)
    //Error, could not send the message

You may use the above code.


Ensure you set SmtpClient.Credentials after calling SmtpClient.UseDefaultCredentials = false.

The order is important as setting SmtpClient.UseDefaultCredentials = false will reset SmtpClient.Credentials to null.


Set the Credentials property before sending the message.


How do you send the message?

The classes in the System.Net.Mail namespace (which is probably what you should use) has full support for authentication, either specified in Web.config, or using the SmtpClient.Credentials property.


To send a message through TLS/SSL, you need to set Ssl of the SmtpClient class to true.

string to = "[email protected]";
string from = "[email protected]";
MailMessage message = new MailMessage(from, to);
message.Subject = "Using the new SMTP client.";
message.Body = @"Using this new feature, you can send an e-mail message from an application very easily.";
SmtpClient client = new SmtpClient(server);
// Credentials are necessary if the server requires the client 
// to authenticate before it will send e-mail on the client's behalf.
client.UseDefaultCredentials = true;
client.EnableSsl = true;