In what context or situation? Please provide more information so I can give you a specific answer.
The phrase "to whom it may concern" is known as a salutation or a formal greeting used at the beginning of a letter or email when the recipient is unknown.
When the pronouns who, whom, whose, which, and that are used to introduce dependent clauses they are relative pronouns.When the pronouns who, whom, whose, and which are used to introduce a question, they are interrogative pronouns.
No, "whom" is not always preceded by a preposition. It is often used as an object of a verb or preposition in formal writing.
Relative pronouns
The word that receives the action of the verb and answers the question "what" or "whom" is called the direct object.
The phrase "to whom it may concern" is known as a salutation or a formal greeting used at the beginning of a letter or email when the recipient is unknown.
A person from Rome is called a Roman.
Amerigo Vespucci
They are called the intended recipient or the addressee.
Adrian Hilton
by whom were you taught english?
A person in whom you confide is often referred to as a confidant or a trusted friend.
Samuel.
The payee
landlord
Iberians, after whom the peninsula is named
her name maybe?