since you are receiving the order through the secondary address, but not the main address, it points to a problem on the smtp server. It suggests that the smtp server is refusing to relay the email for that address.
hpw are you configuring the store emails section? Is the main address set as the CC Address? The secondary address set as the BCC Address? are either of these addresses the same as the From address? Most SMTP Servers will refuse to relay the email if it is going to the same address it came from.
I still suggest contacting the host to have them look in the error is to see why the email is not being relayed.