USPS considers the eBay Standard Envelope (ESE) to be in the metered mail category (the same as most utility bills; credit card statements; and so on) ; thus, there is no "hand-scanning" done by USPS -- the ESE is machine-scanned at either the next USPS Distribution Center (which may be in another city, or even in another county). There is often only one original machine-scan, followed by the final machine-scan, when the ESE is delivered to the post office associated with the ZIP Code on the envelope (NOT the buyer's address!), although there MAY be machine-scans in between, depending upon the number of USPS Distribution Centers through which it is processed.
There is often a one-day delay between the time that the ESEs are marked "Delivered" at the post office associated with the buyer's ZIP Code, and their final destination at the buyer's address.
If you mail the ESEs directly into the "Metered Mail Only" slot in your USPS lobby (rather than handing the ESEs to a postal employee at the post office counter), your ESE will be processed immediately with other metered mail. If you hand the ESE to a postal employee at the post office counter, the counter employee just adds it to a pile of other envelopes, which later has to be hand-sorted to separate metered mail from stamped mail -- which slows down the time for delivery to the USPS Distribution Center.
It all sounds confusing; but just think of the eBay Standard Envelope as being in the same category of mail as your utility bills and credit card statements -- they are all machine-scanned, rather than hand-scanned, and they are treated much differently than packages which have USPS tracking numbers.
Good luck!
