to whom it may concern
Used as a formal salutation in a letter when the writer does not know the recipient or the identity of the recipient.
ADJ.
determined, famous, live, many
I know many people whom I've lost touch with over the years.
VERB + WHOM
decide, discussed, hear, marry, met, ran
I ran into my old friend Sarah yesterday, whom I hadn't seen in years.
WHOM + NOUN
everyone, girls, island, john, poems
I met John, whom everyone on the island seemed to know quite well.
PREP.
into, than, through, with
She had to choose between two candidates, one of whom was more experienced than the other.