Instead of making a memory stream you can write the image as:
using (FileStream fsNew = new FileStream(Server.MapPath(MailFile), FileMode.Create, FileAccess.Write))
{
try
{
fsNew.Write(bytes, 0, bytes.Length);
}
catch (Exception ex)
{
throw ex;
}
}
Also if you are specific to MemoryStream,
flush it before using it.
using (MemoryStream ms = new MemoryStream(bytes, 0, bytes.Length))
{
fileName = Guid.NewGuid().ToString();
ms.Flush();
image = (Bitmap)System.Drawing.Bitmap.FromStream(ms);
MailFile = FolderLocation + fileName + ".png";
image.Save(Server.MapPath(MailFile));
}