This is consistent with most reports I’ve seen of coronavirus longevity on paper and cardboard. Whether it’s necessary or not (who knows?) I’ve gotten into the habit of tossing mail into a box I keep next to the fridge on the kitchen floor until I eventually feel like getting around to it, which is sometimes not for a long time as I tend to forget about it. This also has the side benefit that most of it is bills, which I thereby get to ignore for much longer than usual. 
We were quarantining mail and packages until early April. Based on the news and as the situation developed we shifted to open, toss the packaging, wash our hands. Given that we never decontaminated or quarantined groceries beyond normal washing of produce, it seemed to by a very minor possible vector.
Mail is mostly handled by machines, not people.
What handling there is, is minimal.
I’m cracking up over this, maybe because I’ve never seen our mail carrier, who drives around putting mail in mailboxes. I’m imagining you carrying on, taking advantage of the substitute, who gives out extra junk mail that you have to sit quietly and read.
I’d be happy to throw an eraser at his back.
You cannot absorb virus through your hands. Quarantining inanimate objects should be unnecessary if you dispose of the packaging after opening then wash your hands. Or wear rubber gloves to open them if it’s a great concern.
We’ve never taken any precautions with our mail.
If I’ve gotten a bill, I’m going to be handling that later as I pay it. If there’s virus on the envelope and I open it normally, I’ve just transferred the virus to the contents of the envelope. I’m thinking of those demonstrations where flourescent dye is used as a disease stand-in. The unwitting participants handle a bunch of food and then the ultraviolet light is turned on and they can see where it’s all been spread since they didn’t wash their hands enough.
Of course, if as has been reasonable argued above, if it’s just extremely unlikely that the virus can be transmitted via mail in the first place, this is all moot. Thank you all for your input. I’m considering everything you’ve said, and will definitely reconsider our mail policy.