I just received a letter from the Democratic National Committee.
The front of it stated in big letters - WE'RE SUING DONALD TRUMP I am a registered Republican so how did they get my name and address?
I did not open it but have written Return to Sender on both sides.
OP, did you look at the stamp in the upper right hand corner of the envelope? If it said "Bulk mail" or "nonprofit" the post office will treat it as trash. If it had a first class stamp on it then it will make its way back to the sender, but that is usually a third party middleman. Kinda sucks, but that's how the mail works. Best thing to do is contact the DNC and demand them to rectify this situation.
It's better just to let them keep sending their junk mail to you. Make them waste their money.