Sifting through search engines and Web sites is a daunting task. The goal of email marketing is to find the places where they are meeting and give them the opportunity to contact you. The most obvious place to find prospects is at other Web sites, newsgroups, and mailing lists. This method of marketing still works, but many mailing lists and newsgroups have settled into their own series of experts. It's harder to penetrate market share this way.
Customers have a tough time figuring out who is who.
It would be great to just buy a list of interested customers, as you can in direct mail. Email marketing is still in its infancy online and many of the so-called lists are not tested or even targeted. A sample of the message that was sent, to see if your offer makes sense. Some idea of results generated. You can also buy lists, but be careful.