Despacho el paquete al casillero postal.

Despacho is the first-person singular present indicative form of despachar.

So:

• yo despacho = I dispatch / I send / I ship

In this sentence, it means something like I send/ship the package. Depending on context, the Spanish present can also sound like:

• I send the package (habitual)
• I’m sending the package (right now)
• sometimes even I’ll send the package (near future)

Both can work, but they have slightly different feels.

• enviar is often the most neutral everyday verb for to send
• despachar can sound a bit more like to dispatch, to ship out, or to process for sending

In business, logistics, shipping, or postal contexts, despachar can sound very natural. In casual speech, many speakers might prefer envío.

So:

• Despacho el paquete... = a bit more logistical/formal
• Envío el paquete... = very common and neutral

Because a + el contracts to al in Spanish.

So:

• a + el casillero postal → al casillero postal

This contraction is mandatory in normal Spanish.

A similar contraction happens with:

• de + el → del

Spanish usually needs an article with countable nouns in cases like this.

El paquete means the package — a specific package that the speaker and listener can identify from context.

Compare:

• Despacho el paquete... = I send the package
• Despacho un paquete... = I send a package

Leaving out the article here would sound incomplete or unnatural.

Here, a marks the destination of the package.

With verbs like send, take, bring, or move, Spanish often uses a to show where something goes.

So:

• Despacho el paquete al casillero postal = the package is being sent to the postal box / mailbox / postal locker

This is not the same as the personal a used before people. Here it is simply showing destination.

Usually, it is better to think of al casillero postal here as a destination phrase rather than a classic indirect object.

It tells you where the package is being sent.

That matters because Spanish often uses indirect object pronouns with actual recipients:

• Le despacho el paquete a Ana.
  Here a Ana is a recipient, so le fits naturally.

But with al casillero postal, the phrase is more about location/destination than a person receiving something.

It usually refers to a postal box, P.O. box, or some kind of assigned mail compartment, depending on the country.

Regional vocabulary can vary. In some places, you may also hear:

• apartado postal
• buzón postal

So casillero postal is understandable, but the most common term may change from one Latin American country to another.

Usually, a is the most natural choice here.

Why? Because the sentence is expressing the destination of movement/shipping:

• send something to a place → enviar/despachar algo a un lugar

Para often emphasizes intended recipient, purpose, or for rather than the direct endpoint of movement.

So for this sentence, learners should stick with:

• al casillero postal

Because the direct object is already stated explicitly:

• el paquete

Spanish does not need a direct object pronoun if the noun is already there.

If you wanted to replace el paquete with a pronoun, you could say:

• Lo despacho al casillero postal.

Here:

• lo = it = the package

Yes, but the given order is the most straightforward and natural for learners:

• Despacho el paquete al casillero postal.

That is:

• verb
• direct object
• destination

Other orders are possible for emphasis, but they are less neutral:

• Al casillero postal despacho el paquete.

That can sound marked, contrastive, or stylistically unusual in normal conversation. For everyday use, the original order is the best one to learn first.