Function SendEmail(ByVal ToAddress As String, ByVal FromAddress As String, ByVal MessageSubject As String, ByVal MessageBody As String)
Dim MessageHead As String = "<html><head>"
MessageHead = MessageHead & "<style "
MessageHead = MessageHead & "body {background-color:#F7F7F7; color:#000; font-family:arial,verdana,sans-serif; font-size:12px;}"
MessageHead = MessageHead & "</style></head></body>"
Dim MessageFoot As String = "</body></html>"
MessageBody = MessageHead & MessageBody & MessageFoot
Dim ReturnMessage As String = ""
Dim mm As New MailMessage(FromAddress, ToAddress)
Dim smtp As New SmtpClient
mm.Subject = MessageSubject
mm.Body = MessageBody
mm.IsBodyHtml = True
Try
smtp.Host = "0.0.0.0" 'ADD HOST IP
smtp.Send(mm)
ReturnMessage = "La mail è stata inviata"
Catch ex As Exception
ReturnMessage = "Spiacente, c’è stato un problema! " &amp; ex.Message
End Try
SendEmail = ReturnMessage
End Function

last [VB.NET] : Inviare una mail in formato HTML