public void Message_WithXReceiverSetByUser_ShouldNotClearXReceiverHeader()
{
_message.Headers.Add("X-Receiver", "[email protected]");
_message.From = new MailAddress("[email protected]");
_message.To.Add(new MailAddress("[email protected]"));
_message.HeadersEncoding = Encoding.UTF8;
_message.PrepareEnvelopeHeaders(true, false);
Assert.NotNull(_message.EnvelopeHeaders.GetValues("X-Receiver"));
_message.EncodeHeaders(_message.EnvelopeHeaders, false);
_message.EncodeHeaders(_message.Headers, false);
Assert.Equal(1, _message.EnvelopeHeaders.GetValues("X-Receiver").Length);
Assert.Equal(1, _message.Headers.GetValues("X-Receiver").Length);
}