The linked article claims that an e-mail can be deleted from the recipient's email in-box, regardless of whether the recipient is running a Pluto client.
Earth to Pluto ... assuming the received e-mail is a classic plain-text e-mail, that's impossible. Either the recipient is running a Pluto-compliant client, in which case the claim is true, or the recipient is not running a Pluto-compliant client, in which case the claim is false.
The only way this could work is if the received e-mail has content linked to Pluto's site (example would be an HTML e-mail containing an iframe with hosted content), where the real e-mail is located. So ... they should be honest and say that.
Earth to Pluto ... assuming the received e-mail is a classic plain-text e-mail, that's impossible. Either the recipient is running a Pluto-compliant client, in which case the claim is true, or the recipient is not running a Pluto-compliant client, in which case the claim is false.
The only way this could work is if the received e-mail has content linked to Pluto's site (example would be an HTML e-mail containing an iframe with hosted content), where the real e-mail is located. So ... they should be honest and say that.