I captured a pic of that info off of a Fox News graphic, so it sits on my cell phone as reference ongoing.
In our effort to stop nasties at our door after we pickup packages and mail we deposit them just inside the doorway, write the letter of the day of the week (M, T, W, R, ...) on the front with a Sharpie, and wash hands immediately.
Based upon the study Doug references, letters, cardboard boxes, ... sit for 24 hours before opening.
There is some concern about plastic stuff inside the boxes, but so far we've not addressed that. Probably should. With small stuff Clorox wipes are probably the easiest, but we've been trying to conserve use since who knows how long before we'll be able to get more.
Plastic envelopes either sit for 3 days, or gets Lysoled before opening. We tend to prefer the 3 days so whatever is inside also waits ... plus the flowery Lysol smell drives me crazy.
I'll admit that we don't do much to clean up groceries when they come in the door besides washing hands. Most of it sits on shelves or in the fridge for a few days before we use it anyway, plus we assume it sat on a shelf at the store for a little while - possibly less than 24 hours though. We've not heard/seen if the store is using extra sanitation measures. It's a VERY small family owned store.
On a VERY side and sad note, today I read about two smallish studies (n=100 & 18) that show that about 2/3's of COVID-19 patients who get put on a ventilator do not come off alive (don't survive). That sucks.
With me being 60 and my wife a young 63, we're taking this very seriously and doing our best to avoid the virus until a vaccine is available.