Wǒ jīntiān shōudào le yíge kuàidì, kěshì bāoguǒ shang de dìzhǐ bú duì.

了 marks a completed action here. 收到 means to receive, and 收到了 means received / have received.

So:

• 我今天收到一个快递 = I receive a package today / I received a package today
• 我今天收到了一个快递 = I received a package today, with clear emphasis that the receiving actually happened

In this sentence, 了 helps show that the package has already arrived.

收 means to receive / to accept in a general sense.
收到 often emphasizes successfully receiving something.

Compare:

• 我收快递。 = I receive deliveries / I accept packages
• 我收到了快递。 = I received the package

The 到 in 收到 often adds the idea of reaching the result.

Both are possible.

• 我今天收到了一个快递。
• 今天我收到了一个快递。

Chinese is flexible with time words like 今天. They usually come:

• after the subject: 我今天...
• or at the beginning of the sentence: 今天我...

Both are natural.
我今天... keeps the focus slightly more on I.
今天我... can make today a bit more prominent.

个 is a measure word. In Chinese, when you say one + noun, you usually need a measure word.

So:

• 一个快递 = one delivery / one package

The pattern is:

• 一 + measure word + noun

Here, 个 is a very common general measure word.

This is because of tone sandhi.

一 is normally first tone: yī.
But before a fourth-tone syllable, it changes to second tone: yí.

Since 个 is pronounced gè in dictionary form, we get:

• 一个 → yíge

In normal speech, 个 is often lighter, almost neutral, but learners usually still memorize the phrase as yíge.

They are related, but not exactly the same.

• 快递 often means express delivery, courier delivery, or even the delivered item in everyday speech
• 包裹 means package / parcel

So in this sentence:

• 收到一个快递 = received a delivery / a delivered package
• 包裹上的地址 = the address on the package

Using both is natural. The first part talks about the delivery item in everyday terms, and the second part refers specifically to the physical package.

可是 means but or however.

In this sentence, it connects two ideas:

• I received a package today,
• but the address on it is wrong.

可是 and 但是 are very similar. Both often mean but.
可是 can sound a little more conversational in many contexts.

So:

• 可是包裹上的地址不对。
• 但是包裹上的地址不对。

Both work.

Literally, it is:

• 包裹 = package
• 上 = on / on top of
• 的 = linking particle
• 地址 = address

So 包裹上的地址 means:

• the address on the package

A helpful way to see it is:

• [package + on + 的] + address
• the address that is on the package

This is a very common Chinese structure.

上 here means on.

Chinese often uses location words like:

• 上 = on
• 里 = in / inside
• 下 = under

Examples:

• 桌子上的书 = the book on the table
• 包里的手机 = the phone in the bag
• 椅子下的猫 = the cat under the chair

So:

• 包裹上的地址 = the address on the package

的 links descriptive information to a noun.

In this sentence, 包裹上 describes 地址:

• 包裹上的地址 = the address that is on the package

You can think of 的 as a connector, often similar to -’s, that is, or just a grammatical linker.

More examples:

• 我的书 = my book
• 红色的车 = the red car
• 桌子上的电脑 = the computer on the table

不对 means not correct / not right. It is very natural for things like:

• addresses
• answers
• numbers
• directions
• names

So 地址不对 means the address is wrong / incorrect.

You could also hear:

• 地址错了 = the address is wrong

That is also natural.
A rough difference:

• 不对 = not correct
• 错了 = wrong / mistaken, often with a stronger sense that an error has occurred

In this sentence, 不对 sounds smooth and natural.

This is another tone sandhi rule.

不 is normally fourth tone: bù.
But before another fourth-tone syllable, it changes to second tone: bú.

Since 对 is fourth tone (duì), we get:

• 不对 → bú duì

This change makes pronunciation smoother.

Yes, but it sounds more formal.

• 地址不对 = very common, natural, everyday speech
• 地址不正确 = more formal, more like the address is incorrect

For normal conversation, 不对 is usually the better choice.

In everyday Mandarin, 快递 can mean both:

1. express delivery / courier service
2. the delivered package itself

So when someone says:

• 我收到一个快递。

it usually means:

• I received a package / delivery.

This is very common spoken usage.

Yes, it can still be grammatical, but the feeling changes.

• 我今天收到了一个快递。 = I received a package today
• 我今天收到一个快递。 = less clearly marked as completed; it may sound less natural in this context

Since the speaker is talking about a completed event and then explaining a problem with the package, 了 is the most natural choice.

Chinese often avoids awkward repetition, just like English.

Here the sentence first introduces the event:

• 收到一个快递 = received a delivery

Then it refers to the physical object more specifically:

• 包裹上的地址 = the address on the package

This sounds natural and clear. Repeating 快递 would be possible in some contexts, but 包裹 fits especially well when talking about something physically written on it.

Yes, it sounds natural and normal.

It is the kind of sentence someone might say when reporting a delivery problem:

• 我今天收到了一个快递，可是包裹上的地址不对。

It is clear, everyday Mandarin, and grammatically standard.