Just the Priority property, the Reply-To header is set via a property called ReplyTo on the MailMessage object. Since the ReplyTo property is of type MailAddress, it can be a simple email address, or it can include a friendly display name.

The following example demonstrates setting the ReplyTo property.

[ C# ]

static void SetTheReplyToHeader()
{
//create the mail message
MailMessage mail = new MailMessage();

//set the addresses
mail.From = new MailAddress("me@mycompany.com");
mail.To.Add("you@yourcompany.com");

//set the content
mail.Subject = "This is an email";
mail.Body = "this is the body content of the email.";

//specify the priority of the mail message
mail.ReplyTo = new MailAddress("SomeOtherAddress@mycompany.com");

//send the message
SmtpClient smtp = new SmtpClient("127.0.0.1");
smtp.Send(mail);
}

[ VB.NET ]

 Sub SetTheReplyToHeader()
'create the mail message
Dim mail As New MailMessage()

'set the addresses
mail.From = New MailAddress("me@mycompany.com")
mail.To.Add("you@yourcompany.com")

'set the content
mail.Subject = "This is an email"
mail.Body = "this is the body content of the email."

'specify the priority of the mail message
mail.ReplyTo = New MailAddress("SomeOtherAddress@mycompany.com")

'send the message
Dim smtp As New SmtpClient("127.0.0.1")
smtp.Send(mail)
End Sub 'SetTheReplyToHeader