Of course “snail mail” also can be someone else’s demand on your time. But, the person sending you an actual letter has the disincentive of having to pay for stationary, an envelope, and postage.
Maybe email senders should have to pay something for sending you an email. It might create a business opportunity too.
Your email service provider could implement a system. They’d get a percentage from charging unsolicited emailers, but you’d get most of the fee. Gmail, Hotmail, or Yahoo could start charging, say, 50 cents to senders for emails sent to your inbox, you’d get 45 cents and they’d pocket 5 cents for their trouble.
Don’t worry, there’d be a friends and family “no charge” list. But emailers who aren’t on that list would be charged to send any unsolicited emails to your inbox. If you got an email from an unrecognized sender that you actually were glad to get, you could waive the fee.
Having to pay would even save the senders money and time too because they wouldn’t be wasting their time composing and sending out frivolous emails.
I think something like this might work, and everyone would come out ahead.