Neither of the 4 causes virus, but keep the following in mind:

1] Noone likes spam. So don’t send mail unless people have given you permission. In some countries it is forbiddin by law to send unsolicitated mail.
2] More and more people block popups
3] Auto repsonder can be handy to handle certain things automaticly, but people prefer a personal msg.
4] Banner exchanges normally only generate money for the ones who host the exchange service. More and more people add banner exchange servers to their black list so they don’t see it.

If you have a online ordering system, just make sure the website is setup easy so people can find their way, submit it to searchengines, and make sure everything is working on the website. If you offer a good product/service for the right amount of money, people will come to you automaticly.