18? Hell! I have been receiving crap mail from AARP for almost 10 years now and my returning their prepaid mailers with nasty comments on why I would never join their socialist, anti-gun organization has fallen on deaf ears....I still get their BS in the mail.
I think I am going to start attaching their prepaid envelopes to bricks and mailing them back.
Mailing of building construction materials is a violation of Postal Regs.
The bricks will simply go into postal trash and with no message delivered to your intended target.