Most people don’t know this but the USPS has their own official stamp for that purpose and any marked or drawn on letters they receive likely go to the trash. Try attaching a sticky note and putting it in the outgoing mail, or talking to the post office directly (although many offices go to great lengths not to give you time).
TLDR: Don’t write on the envelope or it won’t be returned.
Sciaphobia@lemm.ee 5 months ago
I actually bought a stamp that prints that specifically to return Soectrum’s trash.