Sending Email To Different Addresses?

I have created an application and I need to send emails to different addresses. I want to do this inside my application without automating email software like outlook etc. I have used CDO , and different activex like ostrosoft , chilkat etc .But is the same problem : Emails are sended correctly without error messages but :Some emails are received ( like in yahoo adresses), a lot of emails are marked as spam, and all the emails send to hotmail addresses are lost, not received. To send emails I'm using a regular domain, with smtp server, port, user name and password. And when I send emails from the same configuration on outlook express from the same computer, all the emails are received correctly.