The RSendAsMessage has been introduced in Symbian v9 and greatly simplifies the sending of a short messages (SMS) in C++.

// Link against sendas2.lib
#include <rsendas.h>
#include <rsendasmessage.h>

...

 // Open a connection with the SendAs server
 RSendAs saSrv;
 saSrv.Connect();
 CleanupClosePushL(saSrv);
       
// Create your message
RSendAsMessage msg;
msg.CreateL(saSrv, KSenduiMtmSmsUid);
CleanupClosePushL(message);
msg.AddRecipientL(aRecipientNumber,RSendAsMessage::ESendAsRecipientTo);       
msg.SetBodyTextL(aMessageText);
 
// Send the message
message.SendMessageAndCloseL();
       
// Cleanup
CleanupStack::Pop(&message);
CleanupStack::PopAndDestroy(&saSrv);