For years I have been putting a tea bag in their prepaid envelope and dropping it in the mail. Their most recent mailing, which I just received a couple of days ago, had an envelope with a hole in it. I suspect they’re on to us.
I just turned 50 and they have been sending me mailings asking me to join. Each mailing includes a postage paid return envelope. I put a tea bag in each envelope when I get it and throw it in the mailbox. I bought tea bags just for this purpose.