Indirect object pronoun questions

Question

I am making my way through Spanish grammar and still a bit hung up on pronouns, especially with indirect objects.
Question:
For example, this sentence: I write an e-mail to him.
Do I have these parts right?
Subject = I
Verb = write
Direct object = e-mail
Indirect object = him

So, in Spanish it would be: Le escribo un email. (or) Le escribo un email a él.

Part of the book states the following about Indirect object pronouns:
Indirect object nouns or pronouns refer only to people (and to beloved pets); they answer the question “To or for whom is the subject doing something?” An indirect object pronoun can replace an indirect object noun but also is used in Spanish when the indirect object noun is mentioned.

Another question
Do I understand it correctly that IF a sentence has an indirect object that is a person/pet, then it's always correct to use the pronoun for it?

Answer 1

I write an e-mail to him.

Yo escribo un e-mail a él - Yo le escribo un e-mail.

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• El Complemento indirecto indica la persona o cosa a quien va destinada la acción verbal; suele ir precedido de la preposición a. "Blanca compró un libro a sus abuelos"

The indirect object indicates the person or thing to whom the verbal action is intended; It is usually preceded by the preposition a. "Blanca compró un libro a sus abuelos"

• El Objeto Indirecto admite la duplicación con los pronombres átonos (los pronombres personales átonos son aquellos que funcionan como complemento directo o indirecto ) me, te, se, lo, los, le, les, la, las, nos, os, en la misma oración.

The Indirect Object supports duplication with unstressed pronouns (unstressed personal pronouns are those that function as a direct or indirect complement) me, te, se, lo, los, le, les, la, las, nos , os, in the same sentence.

Importante / Important

• Los pronombres que sustituyen al objeto directo son: me, te, lo, la, nos, os, los, las.

The pronouns that replace the direct object are; me, te, lo, la, nos, os, los, las.

• Los que sustituyen al objeto indirecto son: me, te, le, nos, os, les.

Those that replace the indirect object are: me, te, le, nos, os, les.

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El Objeto Indirecto admite la duplicación / Indirect Object supports duplication

Yo escribí un e-mail a mi hermano.

A mi hermano le escribí un e-mail - (A mi hermano escribí un e- mail)

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• Le escribí un e-mail a mi hermano - (Escribí un e-mail a mi hermano).

• Le escribí un libro a mi hermano - (Escribí un libro a mi hermano).

• Le compré un libro a mi hermana - (Compré un libro a mi hermana).

• A ti te duele la pierna - (Te duele la pierna).

• A mí me gusta mucho el deporte - (Me gusta mucho el deporte).