How does one confirm the receipt of an email?

For most Internet email you can't. Internet email doesn't officially support "return receipts", though some email applications do support it. You would have to activate "request read receipts" in Mac OS X Mail:

http://email.about.com/od/macosxmailtips/qt/et_request_recp.htm

and then the receiver's email client would have to support sending the receipt, something most email clients do not.

Regards.

Ask the recipient if he got it. Seriously, that is the only reliable way to know.

Some email applications (not Mail) have an option to add a header to your message that will ask the recipient's application to send a confirmation. But many applications ignore that header, and those that don't normally ask the user for permission before sending.

You cannot force a recipient's computer to respond without his permission. It would be a grave security risk if that were possible. Just include a note asking the recipient to acknowledge receipt. It is the only reliable, and only polite way to do it.

Great question! You can always try 3rd party email tracking services. Do you use Gmail? If so have a look at ContactMonkey and Boomerang. Free services for Gmail. ContactMonkey offers silent email tracking whereas Boomerang offers more of a read receipt where the recipient of your email has to approve the sending of the read receipt.

Hope that helps!

Those services sound like they use remote images (also used by spammers), which wouldn't work if the client doesn't show them.