How to send a mail using HTML format ?......

Hi every one,

    I need to send an email of the purchase details. so, I need to send a mail with HTML format. I have tried  and I am receiving only half of the message body.

    Is there any way to specify the size of the message or any thing wrong with my code.

 Here is the sample code I tried,

            Dim mail As New MailMessage()
            mail.To = TextBox5.Text
            mail.From = "sales@mystrongid.com"
            mail.Subject = "Order has been placed sucessfullty."
            mail.BodyFormat = MailFormat.Html
      ...