I have some connection to that company and would definitely agree with the sibling post that privacy is a huge concern for them. Another interesting thought is

I have some connection to that company and would definitely agree with the sibling post that privacy is a huge concern for them. Another interesting thought is this: All your snail mail metadata is (obviously, but have you recently thought about it?) already available in digital form: No one's reading the addresses by hand on your letters or parcels (unless absolutely necessary, i.e. OCR fails). So they (post services in general) already constantly have to handle the (digital) information of person A sending something to person B, at roughly time X. Feels like smtp.