Physical letters do not obviate scams, nor is the cost that prohibitive. I remember actual 419 scams on blue airmail all-in-one letters back in the 80s. And that was international post too.

Think of it like changing your SSH port. It does nothing to prevent scams per se but you'll have to deal with only 0.00001% of them.

If you build an analogy based on what I get in my mailbox it's more like publishing your email on the internet.

They don't remove it but they do reduce it.

I have an inbox, and I do not receive a lot of scam post. In fact, I don't think I received any since I lived at this address (~10 years ). We do get a few promotional leaflets every other week.

OTOH, I get hundred of spam emails every day.

The former is something which I can handle manually easily, the other is not.

It doesn't have to prevent the scam completely, it just has to make harder for them to scam you than it would be to move on to scam someone else.

If you are targetting a list of well-known authors I guess outsourcing the writing of a couple of hundred handwritten letters shouldn't be too hard. I'm sure they they can find a school class in Nigeria or Kenya who would gladly do it for a few dollars — or a struggling teacher willing to get creative with the homework assignments.

One of my college lecturers only had a physical address on their webpage.

Contact me: letter > envelope > stamp > post box

I think it is a good general principle that, for any process that is likely to be a tempting target for scammers, you should require a non-electronic step to initiate that process. Requiring a physical letter of application for a job, for example.

Uh - there are entire political lobbyist organizations that use something similar to an "autopen" to make mass letters personalized and appear to be handwritten...

Heck - I have seen some in the mail from the "sell your house for cash" companies - typically behind the friendly, "homespun" personable facade, it is a REIT (real-estate investment trust) - or something similar...

(Myself, I can tell that these are mass-generated - but I am (at least also at this point in life - who knows when I get much older) easily able to tell a scam email, phone call or txt-type message - I can typically spot the signs - but those signs are typically there to "weed-out" the people that won't fall for the scam anyways...) - but my non-cynical, non-technical, non-paranoid friends and family need assistance spotting these...)

Or something like European E-Deliveries.

They're "physical letters but digital," tied to a human identity and with proper proof of receipt.