Is thanks a countable noun? Many thanks or much thanks?

A colleague of mine recently wrote in an email "much thanks for your efforts." Does this usage make sense? How does "much thanks" differ from "many thanks"?

This is similar to "Is “Many thanks” a proper usage?"

Much thanks means the same thing as many thanks, but many thanks is the standard form of this phrase, and much thanks is probably merely a corruption of the concept. Basically, thanks is a plural noun (think of each "thank" as an individual expression of gratefulness).

Grammar Girl has a post relating to and pertinently addressing this topic:

..."Which is correct: much thanks or many thanks? I hear much thanks but it just doesn't sound right."

According to the Merriam-Webster Online dictionary, "thanks" is plural, having come from the Middle English singular word "thank." Therefore, "many thanks" is the right phrase because we use "many" with plural count nouns, and we use "much" with mass nouns.

As to popularity, Ngrams, Google searching, COCA, and BNC all concur in that many thanks is vastly more common.

Perusing Google Books led me to a charming passage in a publication of letters to the editor which touches on this topic:

157.--In your article on "Incomparable Wessex, Again," in the May number, I see the expression "Much thanks." Will you kindly tell me if this is correct? Should it not be "Many thanks"?

Undoubtedly it should, though the writer may have had Shakespeare in mind. See "Hamlet," Act I, Scene 1. Still, the expression "Thank you!" or "I thank you!" is always to be preferred to "Many thanks!" or "Thanks!"

In Act I, Scene i of ‘Hamlet’, Francisco says ‘For this relief much thanks.’ That may still be found in modern usage as your colleague has shown, but 'many thanks’ is much more usual. The Corpus of Contemporary English, for example, has 13 records of ‘much thanks’, against 243 of ‘many thanks’.