It is mandatory to use SMTP authentication for sending out emails through our servers. You can use the below sample C# code for the same (by making required modifications):
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SmtpClient smtpClient = new SmtpClient();
MailMessage message = new MailMessage();
MailAddress fromAddress = new MailAddress("from@from.com", "From Name");
// You can specify the host name or ipaddress of your server
smtpClient.Host = "mail.yoursite.com"; //you can also specify mail server IP address here
//Default port will be 25
smtpClient.Port = 25;
NetworkCredential info = new NetworkCredential("smtpuser@yoursite.com", "smtp-password");
smtpClient.DeliveryMethod = SmtpDeliveryMethod.Network;
smtpClient.UseDefaultCredentials = false;
smtpClient.Credentials = info;
//From address will be given as a MailAddress Object
message.From = fromAddress;
// To address collection of MailAddress
message.To.Add("to@domain2.com");
message.Subject = "Your subject";
// CC and BCC optional
// MailAddressCollection class is used to send the email to various users
// You can specify Address as new MailAddress("admin1@yoursite.com")
//message.Bcc.Add("bcc@yoursite.com");
//Body can be Html or text format
//Specify true if it is html message
message.IsBodyHtml = false;
// Message body content
string ss_body = "body of email is here";
message.Body = ss_body;
// Send SMTP mail
smtpClient.Send(message);
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