You can't get tracking on letters, I believe. Anyway, you get tracking for free when you print your own postage, say with PayPal. I pay $2.66 when I print my postage/shipping label: good for 1 to 4 ounces; get free tracking; get a discount; and don't have to worry about a post office along the way hitting the recipient with "postage due." Of course, if it is a relatively inexpensive chip(s), you can breathe easy and self insure, in effect.

From Post Office's "Notice 123" ( https://pe.usps.com/cpim/ftp/manuals/dmm300/Notice123.pdf )

Robert