Send saved email activity / Message form crm 4.0 / 3.0

private void SendEmail(Guid emailActId)
{

#region Create and SendEmail request.
SendEmailRequest req = new SendEmailRequest();
req.EmailId = emailActId;
req.TrackingToken = "";
req.IssueSend = true;

// Send the email message.
SendEmailResponse res = (SendEmailResponse)service.Execute(req);
#endregion

}