They are suggesting to add a footer to outbound emails that says something like “My privacy was preserved when sending this email by 33Mail. Sign up to 33Mail for free to hide your email address and stop spam”
The more I think about this, the less I like it. the whole point of 33mail is to hide your email address, if you're sending out emails that say "hey this isn't even my real email address, gotcha!" that may not go over well.
