Learn Spanish (Latin America): El asistente a quien le doy el mensaje es un contacto importante. - The assistant to whom I give the message is an important contact.

In Spanish, when a relative pronoun (like "who" or "whom") refers to a person and comes right after a preposition (like a, de, con, or en), we must use quien (singular) or quienes (plural). Here, the preposition is a (to), so we use a quien (to whom).

Why is there a le before doy? Doesn't a quien already tell us who is receiving the message?

It does, but Spanish has a very common rule! Whenever an indirect object (the person receiving the action) is mentioned, Spanish often requires us to include the matching indirect object pronoun anyway. Here, le points right back to el asistente. It feels redundant in English, but it is completely natural and expected in Spanish.

Would the word asistente change if the assistant were a woman?

The noun asistente itself would stay exactly the same. Because it ends in -e, it is used for both men and women. To show that the assistant is a woman, you just change the article in front of it to the feminine form: la asistente.

Why is it contacto importante and not importante contacto?