System.Net.Mail.Message.PrepareEnvelopeHeaders C# (CSharp) Method

        internal void PrepareEnvelopeHeaders(bool sendEnvelope, bool allowUnicode)
        {
            if (_headersEncoding == null)
            {
                _headersEncoding = Encoding.GetEncoding(MimeBasePart.DefaultCharSet);
            }

            EncodeHeaders(EnvelopeHeaders, allowUnicode);

            // Only add X-Sender header if it wasn't already set by the user
            string xSenderHeader = MailHeaderInfo.GetString(MailHeaderID.XSender);
            if (!IsHeaderSet(xSenderHeader))
            {
                MailAddress sender = Sender ?? From;
                EnvelopeHeaders.InternalSet(xSenderHeader, sender.Encode(xSenderHeader.Length, allowUnicode));
            }

            string headerName = MailHeaderInfo.GetString(MailHeaderID.XReceiver);
            EnvelopeHeaders.Remove(headerName);

            foreach (MailAddress address in To)
            {
                EnvelopeHeaders.InternalAdd(headerName, address.Encode(headerName.Length, allowUnicode));
            }
            foreach (MailAddress address in CC)
            {
                EnvelopeHeaders.InternalAdd(headerName, address.Encode(headerName.Length, allowUnicode));
            }
            foreach (MailAddress address in Bcc)
            {
                EnvelopeHeaders.InternalAdd(headerName, address.Encode(headerName.Length, allowUnicode));
            }
        }