"Whom" is grammatical, but rarely used unless the preposition is immediately before it. You will hear the first sentence used many, many times more often than the second.
Colloquially, "who" is often used in this way.
Grammar Geek "Whom" is grammatical, but rarely used unless the preposition is immediately before it. You will hear the first sentence used many, many times more often than the second.
To paraphrase that quote attributed to Mr. Churchill - He is the type of person up with whom I will not put :)