public MessageHeader()
{
// Create empty lists as defaults. We do not like null values
// List with an initial capacity set to zero will be replaced
// when a corrosponding header is found
this.To = new MessageAddresses();
this.Cc = new MessageAddresses();
this.Bcc = new MessageAddresses();
this.Received = new List<String>();
this.Keywords = new List<String>();
this.InReplyTo = new List<String>();
this.References = new List<String>();
this.DispositionNotificationTo = new MessageAddresses();
this.UnknownHeaders = new NameValueCollection();
}