I'm not sure how to link to another message here, but I posted an answer recently, that explains the difference. It depends on the code you are using. If you are using CDO1.21 (which requires an authentification and configuration), that may be the problem. But normally CDO2.0 does not need authentification (nor does it need an actual "real" sender)
Thread ID:964917
Message ID:969551

>Hi, I'm not even sure how to find this out. I never worked with CDO before.