Chính sách đổi trả ở trong email.

• chính sách = policy
• đổi = exchange
• trả = return

Together, đổi trả is a common retail/business expression meaning exchange and return. So chính sách đổi trả means return and exchange policy, or more naturally in English, return policy depending on context.

It usually refers to store rules about whether customers can return or exchange items.

Because Vietnamese noun phrases usually put the main noun first and the describing element after it.

So:

• chính sách đổi trả = policy for returns/exchanges

This is the opposite of common English order. English says return policy, but Vietnamese says something closer to policy return/exchange.

A few similar examples:

• cửa hàng quần áo = clothing store
• vé máy bay = airplane ticket
• luật giao thông = traffic law

Vietnamese often leaves out to be in simple statements, especially when the meaning is clear from context.

So:

• Chính sách đổi trả ở trong email.

is understood as:

• The return policy is in the email.

You generally would not use là here. Là is mainly used for identification or classification, such as:

• Đây là email của tôi. = This is my email.
• Anh ấy là giáo viên. = He is a teacher.

For location, Vietnamese usually uses a location phrase directly, or a verb like ở, nằm, or có, depending on style.

Ở trong means in or inside.

The two parts are:

• ở = at, in, located at
• trong = inside, in

Together, ở trong emphasizes location inside something.

However, in this sentence, many speakers would feel that ở trong email is understandable but slightly less natural than just:

• trong email
• nằm trong email
• có trong email

With physical places, ở trong sounds very normal:

• ở trong nhà = in the house
• ở trong phòng = in the room

With something like email, trong email is often more natural.

It is understandable, and a learner may hear or say it, but many native speakers would prefer a more natural version such as:

• Chính sách đổi trả nằm trong email.
• Chính sách đổi trả có trong email.
• Chính sách đổi trả được ghi trong email.
• Trong email có chính sách đổi trả.

The difference is mostly about style and naturalness:

• nằm trong = located in, found in
• có trong = present in, included in
• được ghi trong = written/stated in
• Trong email có... = there is ... in the email

So the original sentence is not wrong, but it may sound a bit literal.

Usually, by itself, that sounds more like a noun phrase than a full sentence.

It can feel like:

• the return policy in the email

rather than:

• The return policy is in the email

If you want a complete sentence, it is better to say one of these:

• Chính sách đổi trả nằm trong email.
• Trong email có chính sách đổi trả.
• Chính sách đổi trả có trong email.

That said, in conversation, short elliptical phrases are common. If someone asks:

• Chính sách đổi trả ở đâu? = Where is the return policy?

you might hear a short answer like:

• Trong email. = In the email.

Vietnamese does not have articles like English a, an, and the.

So chính sách đổi trả can mean:

• a return policy
• the return policy

The exact meaning depends on context.

In this sentence, because both speaker and listener already know which policy is being discussed, English naturally uses the:

• The return policy is in the email.

But Vietnamese does not need a separate word for that.

Yes. Vietnamese often allows different word orders depending on what you want to emphasize.

Here are some natural alternatives:

• Chính sách đổi trả nằm trong email.
  Focuses first on the return policy.

• Trong email có chính sách đổi trả.
  Focuses first on the email or the location.

• Email có chính sách đổi trả.
  Means The email contains the return policy.

All of these are natural, but they are not exactly identical in emphasis.

Yes, email is very commonly used in everyday Vietnamese.

There is also a more formal/native-style term:

• thư điện tử = electronic mail

But in normal speech and writing, most people simply say email.

So:

• trong email is very normal
• trong thư điện tử is correct but sounds more formal or official

It usually covers both ideas:

• đổi = exchange
• trả = return

So chính sách đổi trả is broader than just a refund rule. It often includes things like:

• whether you can exchange a product
• whether you can return it
• time limits
• conditions for damaged or unopened items

If a business specifically wants to talk about refunds, it might use something more specific, such as:

• chính sách hoàn tiền = refund policy

So đổi trả is a useful general retail term, not just one single action.