Apparently they want you to collect these packets in boxes and mail them via UPS.I also can't imagine the USPS is particularly keen on a bunch of soggy #10 envelopes clogging up their machinery with leaking taco sauce.
This sounds rather insane.
Taco Bell® Sauce Container Free Recycling Program | TerraCycle
TerraCycle and Taco Bell® have partnered to create a free recycling program. Send in your empty sauce packets and containers waste, and we’ll recycle it.
www.terracycle.com