My first witness of similar experience was 4 certified letters mailed return receipt to various addressees at a local court

try to keep up this is tricky


upon my trip to the post office to pick up the receipts I was handed 3 of the letters back undelivered

and all four signature cards

one letter had its signature card stripped off and another, from the one missing letter taped in its place

So, one of the entities received their copy, but I had no record

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That was the 1st time

In another state, another time, local court again, using the tracking only, no signature cards, the tracking
at two different intervals came up with something along the lines of "delivery error"

however, one of those instances a Judge personally wrote me back, even politely corrected some of my poor grammar, despite the "delivery error"