In article , Ken Hart
wrote:

it is legal to take pictures inside a post office in unsecured public areas
you have no right to privacy in public if you do not want your picture
taken stay home with curtians drawn


there is a sign in every postoffice that states this


Refer to US Postal Service bulletin 22228.
https://about.usps.com/postal-bullet.../info_005.html

There are three types of filming/recording referenced in this bulletin:
News, Film & TV Production, and Personal Use.

I assume you mean personal use photos.
"Informal snapshots from handheld cameras for personal use may be
allowed at the postmaster¹s discretion provided that there is no
disruption to Postal Service operations and that the pictures are taken
from areas accessible to the public. In these cases, no prior
permis-sion is required from the Office of Rights and Permissions;
however, no lighting or scaffolding may be set up, and no picture can
depict any Postal Service employee, customer, security camera, or cover
of mail (i.e., the exterior of a mail-piece, which would show customer
name and address among other things). Postmasters may restrict any and
all photography if they determine that it is disruptive or there are
potential security concerns."

While you do have a reduced expectation of privacy in a public place,

there is no expectation of privacy in a public place.

your mail is private.

nobody is suggesting people take photos of other people's mail.

By extension, the act of acquiring your mail would
also be private, so no pictures of customers.

false. there is nothing private about going to the post office and
getting mail.

photos of customers are among what's prohibited, except that it's
impossible to enforce it.

The postal employees are in a workplace, so they have an expectation of
privacy.

not when they are public facing, however, that doesn't matter since
it's among what's prohibited.

The post office building has to be secure, so no photos of security
features.

also listed as prohibited.