This idea has been around for a long time and most recently championed by Esther Dyson with the aim of tackling email overload.
My initial version is to used as an incentive to get a reply to an email as how many of us have emailed people but don't get a response, quite a few of us I'm sure.
How it works is you type in the recipient's email address at senderpays.co and that'll create an email address which you can copy to your email client or just click the links for Gmail, Hotmail or Yahoo to immediately compose your message.
After you send it you'll get an email back requesting payment, click the link, select either $5, $10, $25, $50 or $100 as the incentive, pay using PayPal and that's it! If however you don't get a reply within 7 days then you get a full refund.
If you do get a reply then it all works over email without requiring any logging in to websites or any of that nonsense.
The topic of the sender paying has received quite a bit of flak but I think it's been misrepresented as it's not about postage like paying to send an email which should remain free but it's the valuing of the recipients' time which is finite. Email allows anyone access which leads to email overload and in some cases email bankruptcy leaving the senders without a response.
Pay the Recipient and Get Noticed is my view, it's fair and a win-win since the recipient get's compensated and the sender gets a response, which is what we want anyway!