HOWTO: Set the Default Reply-Recipient with CDO Using C++

   #import "cdo.dll" no_namespace
   #include <stdio.h>
   #include <MAPIUTIL.H>
   
   int main(int argc, char* argv[])
   {
     CoInitialize(NULL);
     try {
        // Uncomment one of the next two lines of code as appropriate:
        // Create a MAPI.Session pointer with CDO (1.1)
        // SessionPtr pSession("MAPI.Session");
        // or Create a MAPI.Session pointer with CDO (1.2, 1.21)
        //_SessionPtr pSession("MAPI.Session");

        _SessionPtr pSession("MAPI.Session");
        pSession->Logon();
        FolderPtr pInbox = pSession->Inbox;
        FolderPtr pOutbox = pSession->Outbox;
   
        // get the first message from the Inbox
        // 
        MessagesPtr pMessages = pInbox->Messages;
        MessagePtr pMessage = pMessages->GetFirst();
   
        // save the sender of this message for the later use
        AddressEntryPtr m_pReply = pMessage->Sender;
   
        // create a new message in the Outbox
        // 
        MessagesPtr pNewMsgs = pOutbox->Messages;
        MessagePtr pNewMsg = pNewMsgs->Add();
   
        // set some properties of the new message
        pNewMsg->Subject = "Set default reply-recipient";
        pNewMsg->Text = "Set up two Cdo properties";
   
        // Create a recipient
        RecipientsPtr pRecipients = pNewMsg->Recipients;
        RecipientPtr pRecipient = pRecipients->Add();
   
        // Set properties of the new recipient
        pRecipient->Name = <your name goes here>; // a string
        // Type can be ActMsgTo, mapiTo or CdoTo for different CDO versions
        // They all have constant value of 1.        
        pRecipient->Type = (long) mapiTo;
   
        // Resolve the recipient address
        pRecipient->Resolve();
   
        // set the default reply-recipient of pNewMessage to be the
        // Sender of pMessage
        FieldsPtr pFields = pNewMsg->Fields;
   
        // set up a text string that matches the binary signature of the
        // FLATENTRYLIST structure
        char FlatLength[200] = "";
        wsprintf(FlatLength, "%x",
            strlen((char *)(bstr_t)m_pReply->ID)/2 );
        strcat(FlatLength, "000000");
        strcat(FlatLength, (char *)(bstr_t)m_pReply->ID);
   
        char StructLength[200] = "";
        wsprintf(StructLength, "%x", strlen(FlatLength)/2 );
   
        char m_Entry[200] = "";
        strcat(m_Entry, "01000000");
        strcat(m_Entry, StructLength);
        strcat(m_Entry, "000000");
        strcat(m_Entry, FlatLength);
   
        // Set the two pertinent properties
        pFields->Add((long)CdoPR_REPLY_RECIPIENT_ENTRIES,
                 (variant_t)m_Entry);
        pFields->Add((long)CdoPR_REPLY_RECIPIENT_NAMES, m_pReply->Name);
   
        // send message with UI
        pNewMsg->Send(true, true);
   
        // or send message without UI
        // pNewMsg->Send(false, false);
   
       } catch (_com_error) {}
   
       CoUninitialize();
   
     return 0;
   }