Redundant Object Pronouns
 

Redundant Object Pronouns

Reading a few articles they state that you have to use an Indirect Object Pronoun even if the Indirect Object is named in the sentence.
Also they state "even when you identify the person by name, you must still use an Indirect Object pronoun"

So in the following 3 examples is only example 2 allowed? Is example 1 incorrect and not allowed?

I send the letter to Juan
1) Yo envio la carta a Juan
2) Yo le envio la carta a Juan

I send the letters to my friends
1) Yo envío las cartas a mis amigos
2) Yo les envío las cartas a mis amigos

The teacher reads the book to the children
1) El maestro lee el libro a los niños
2) El maestro les lee el libro a los niños

Thanks,
Andy

Both are correct, but usage depends on the region and the speaker.
In Mexico we only use number 2, but in Spain many people tend to prefer number 1.