It’s not practical but it’s easy to target a few interesting individuals.

Also it’s inconvenient to encrypt and decrypt physical mail.

The constitution of some countries in the West includes the privacy of correspondence. Idk how many countries and how that privacy is interpreted in any particular cases.

IMO it should be argued, in the Europes, that this covers electronic correspondence too, and thus ChatControl and its ilk are unconstitutional.

USPS has something called a “Mail Imaging program”, where they photograph the outside of every piece of mail that goes through their system. They use it to process the mail, but law enforcement does request copies of all stored images related to people and addresses they’re investigating.

They also have the “Mail Covers program”, where law enforcement will proactively request USPS to monitor and forward information on all mail to and, as far as possible, from a given person or address. That information is limited to the outside of the envelope but, if they see something they deem suspicious, they can get a warrant to open the mail. I’ll also note that privacy guardrails on the program are notoriously lax: something like 20% of covers were approved without the necessary paperwork, and 15% weren’t adequately justified.

If you’re wondering what the big deal with getting data from the outside of the envelope is, you might be interested in “Finding Paul Revere”.

In the days of old people would cover both sides of a letter with writing and then tri-fold it before putting it in an envelope. this makes it much harder to read it through the envelope (by holding it up to a light).

1. physical mail has gotten way more expensive, now 78 cents for a regular letter and $5 for a small package. So it adds up. I probably send a dozen emails a day while sending out maybe 3 envelopes per month, usually stuff like bill payments or business docs, rather than personal letters.

2. they collect all the metadata now, i.e. photographs of the front and back of the envelope. I try not to write return addresses on envelopes but sometimes it’s necessary and sometimes I forgot to omit it. They do get delivered without the return address, though I don’t have enough samples to say the reliability is any different.

I do wonder whether the mailbox you drop the letter in somehow gets recorded in the metadata. Obviously the originating post office is recorded, but if there are a dozen mailboxes in the neighborhood and some USPS worker empties them out once a day, idk if there’s any effort to separate the letters by what mailbox they came from, or if they all just get dumped into a large bin.

There was supposedly a snail mail remailer network operating in Poland in the 1950s or so. If you were in Minsk and wanted to correspond with your friend in Pinsk without the KGB knowing, you’d instead send your letter to someone in Poland who would then forward it in a different envelope to Pinsk. I believe some samizdat manuscripts also circulated that way.

would governments be able to surveil everyone? (Is it practial?)

The GDR has done it.

There were no computers at that time. All mail was physical. They did not surveil really everyone, but many targeted people, and presumably all letters from/to the West.

Today with strong computers and AI to scan through all texts, even hand writing, it would be feasable to do even more than that.

It would work until it didn’t.

Just depends how long it takes them to realize it’s happening.

It would certainly make their job harder. We could go back to invisible ink and writing by hand.