Does 1st class mail have tracking?

Does 1st class mail have tracking?
Why can't I track a USPS First Class Large / Flat Envelope shipment ...
Jun 3, 2019

First Class Package: This service includes a package type we refer to as a "Thick Envelope (3/4")". ... Even though USPS does not include tracking on the very cost efficient First Class "Large/Flat Envelope", they do return an unusable reference number when a label is purchased.

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