An Internet service is about to test the frontiers of e-mail privacy., which will launch Monday, allows anyone to secretly track e-mails they send.

You’ll see whether someone opens your e-mail, how long the recipient keeps it open — even where geographically the recipient is reading it.

The reaction could be harsh. “It will freak people out,” says Internet expert Esther Dyson.

“It violates our electronic space in a way that’s as uncomfortable as someone violating our physical space,” says Mitchell Kertzman, a partner at technology investment firm Hummer Winblad. “Add this company to the long list of people who are making the Internet a less attractive place to live and work.”

The service comes from Rampell Software of Cambridge, Mass. will cost $50 a year. You register on the Web site, and then every time you send an e-mail, you add to the end. An e-mail address would look like this: [email protected]

More here.