... We received a certified letter but the postman forgot to obtain our signature ...
For registered mail (decades ago and, probably, today), letter carriers signed for each individual registered item, as did every clerk who handled that registered item along the way.
For certified mail, a clerk noted the total number of "certs" they passed to each letter carrier each day, and that was that. At the end of your tour, you dumped the signed receipts (and undelivered certs) at the clerk's window, and that was that.
Why so casual? Certification fees were low, the amount of time it took for a letter carrier to hand-deliver each cert was high, the number of times that a sender ever complained about a missing receipt was infinitesimal, and the post office was not on the hook for the value of a missing cert.
Once every couple of months, a registered item (always
from a foreign country) would just show-up in the mail stream like any other piece of mail.
But every couple of days
- on some routes, just about every day - a certified item (of domestic origin) would just show-up in the mail stream like any other piece of mail.
noticed the 'cert', we might collect the signature, or not ... nobody in management really cared, and I suspect most of us rather liked treating our customers better than, say, their creditors.