The return email address when using a Hotmail account

Ok, so I have this code:

//  Set the SMTP server.
mailman.put_SmtpHost("smtp.live.com");

//  Set the SMTP login/password (if required)
mailman.put_SmtpUsername("xxx");
mailman.put_SmtpPassword("yyy");

//  Connect to SMTP port 465 using TLS.
mailman.put_SmtpSsl(true);
mailman.put_SmtpPort(25);

But, my account uses email aliases. So, I do this:

//  Create a new email object
CkEmail email;

email.put_Subject("Monthly workbook data");
email.put_Body("Please find attached the latest monthly workbook data.");
email.put_From("Andrew Truckle <ccc>");
success = email.AddTo("PTS Support", "ddd");
//  To add more recipients, call AddTo, AddCC, or AddBcc once per recipient.

The email sends through OK. But when I hit reply, it is going to xxx. It has not honoured the alias ccc I had specified. Why is this?