No, to whom.
This is one of those grammar quibbles that people often don’t get, and I understand that. In the minds of many, the word whom is superfluous. It’s a relic from English’s virtually extinct dative case. There’s no clear grammatical reason to keep it in the language, except that it serves to distinguish the subject of a sentence from the direct object (if that was even in question to begin with). It also makes you sound kind of classy, but only if you use it correctly. There are about a billion grammar-focused websites that will teach you how to use who and whom, but perhaps none with as much humor as The Oatmeal.
So, to summarize what a billion websites will tell you, use who as a stand-in for the subject of a sentence, and whom for the direct or indirect object. In other words, if you’re asking about somebody that is doing something, use who. Example: Who thinks Nerdy Jokes is the greatest blog in the Universe? If you’re asking about somebody that is having something done or given to them, use whom, as in: Whom should I congratulate for writing the fantastic blog Nerdy Jokes?
One oft-suggested trick is to answer the question using the pronoun he or him. If he sounds more correct, then use who when asking the question. If him sounds more correct, use whom.
Who thinks Nerdy Jokes is the greatest blog? He does. (It would sound wrong to say “Him does.”)
Whom should I congratulate? Congratulate him. (You wouldn’t say “Congratulate he.”)
This joke contains the preposition to. A preposition is a word that expresses a relationship between things. The old elementary school mnemonic is this: many prepositions can describe the relationship between a caterpillar and an apple. A caterpillar can go to, from, around, through, inside, above, below, etc, an apple. The noun that follows a preposition is called the object of the preposition, and it follows the same rules as the direct object of a sentence. If you have to decide whether to use who or whom after a preposition, it’s always whom.
To whom should I address this correspondence expressing my admiration for the blog Nerdy Jokes?
You get the idea.