Wiktionary
kindest regards
n. (context idiomatic English) (non-gloss definition: Used as a polite closing of a letter)
Usage examples of "kindest regards".
We talked about you a great deal, and they hoped you might come over soon - sent everything proper, of course, kindest regards - kisses, I believe, from the girls.
Would you be good enough to pass on my kindest regards to Uncle Ernest?