Learn French: Nous la lui faisons envoyer. - We are having him send it.

In the causative faire construction, object pronouns must go before the conjugated verb (faire), not the infinitive. Even though "it" and "him" logically belong to the action of sending (envoyer), they get pulled to the front of the whole phrase to make Nous la lui faisons envoyer. You cannot put them between the two verbs.

Why do we use the indirect object pronoun lui for "him" when he is the one doing the sending?

This is a special rule for the causative faire. If the infinitive verb (envoyer) has a direct object (here, la), the person performing the action (the agent) gets "bumped" to an indirect object role. Since the sentence already has a direct object, "him" is forced to become the indirect object lui.

Would the order of the pronouns change if the sentence meant "We are having me send it"?

Yes! The standard double pronoun order still applies to causative sentences. First- and second-person pronouns like me always come before direct objects like la. So, "We are having me send it" would be Nous me la faisons envoyer. But because both pronouns in our current sentence are third-person, the direct object (la) must come before the indirect object (lui).

Could this sentence also mean "We are having it sent to him"?