N-ar trebui să deschizi mesajul fără să verifici cine l-a trimis.

N-ar trebui is the contracted form of Nu ar trebui and means should not.

• nu = not
• ar trebui = should / would have to / ought to

The hyphen shows that nu has been shortened to n- before ar. This contraction is very common in Romanian, especially in everyday writing and speech.

So:

• Nu ar trebui să deschizi...
• N-ar trebui să deschizi...

mean the same thing.

Romanian often expresses should / ought to with ar trebui.

Literally, a trebui means something like to be necessary / to have to, and ar trebui is the conditional form. In practice, though, it is the normal way to say should in many situations.

Examples:

• Ar trebui să pleci. = You should leave.
• N-ar trebui să faci asta. = You shouldn’t do that.

So even though it may look more like would have to word-for-word, the natural English translation is often simply should.

After ar trebui, Romanian normally uses să + verb.

So:

• ar trebui să deschizi = you should open
• ar trebui să verifici = you should check

This is a very common pattern in Romanian. English uses the bare infinitive after should (should open), but Romanian does not do that here. Romanian prefers the să construction.

Deschizi is the 2nd person singular form, used for you.

The verb is a deschide = to open.

Here are some present/subjunctive-related forms:

• eu deschid = I open
• tu deschizi = you open
• el/ea deschide = he/she opens

Because the sentence is addressing you, Romanian uses deschizi.

Because Romanian often puts the definite article at the end of the noun.

• mesaj = message
• mesajul = the message

This is one of the most important features of Romanian grammar. Instead of a separate word like English the, Romanian usually attaches it to the noun.

Other examples:

• carte = book
• cartea = the book
• băiat = boy
• băiatul = the boy

Romanian usually expresses without doing something with fără să + verb.

So:

• fără să verifici = without checking
• literally: without that you check

English often uses without + -ing, but Romanian does not usually use that same structure. The normal Romanian pattern is:

• fără să pleci = without leaving
• fără să spui = without saying
• fără să mă anunți = without informing me

So in this sentence, fără să verifici is the natural Romanian way to say without checking.

Because să is also used after certain expressions, including fără when Romanian means without doing something.

So the sentence has:

• ar trebui să deschizi → after ar trebui
• fără să verifici → after fără

These are two separate grammar patterns. The repeated să is normal.

It means who sent it.

Breakdown:

• cine = who
• l- = it / him (direct object pronoun)
• a trimis = sent / has sent

So literally it is something like:

• who it sent

But in natural English, that becomes:

• who sent it

Here, it refers to mesajul (the message).

L-a is made of two parts:

• l- = a short direct object pronoun meaning him or it
• a = auxiliary used in the past tense (perfectul compus)

So:

• l-a trimis = sent it / sent him

In this sentence, l- refers to mesajul, so it means it:

• cine l-a trimis = who sent it

The pronoun appears before the auxiliary, which is normal Romanian word order.

Because l- is used for masculine singular direct objects, and that can refer to either:

• a masculine person (him), or
• a masculine thing (it)

Since mesaj is a masculine noun in Romanian, the pronoun used for it is l-.

Compare:

• Băiatul? Cine l-a chemat? = The boy? Who called him?
• Mesajul? Cine l-a trimis? = The message? Who sent it?

So the same form can mean him or it, depending on context.

Because a trimis is the compound past tense (perfectul compus) of a trimite = to send.

• trimite = sends / is sending
• a trimis = sent / has sent

So:

• cine îl trimite? = who sends it?
• cine l-a trimis? = who sent it?

In your sentence, the action of sending happened before the action of opening/checking, so the past tense is used.

No, it is not stated explicitly, but it is understood from the verb form.

Romanian often drops subject pronouns when the verb already makes the subject clear.

• deschizi clearly shows you (singular)
• verifici also clearly shows you (singular)

So tu is unnecessary here, though you could add it for emphasis:

• Tu n-ar trebui să deschizi mesajul...

That would sound more emphatic, like You really shouldn’t open the message...

It is informal singular, because of deschizi and verifici, which match tu.

If you wanted to address someone formally or plural you, you would use:

• N-ar trebui să deschideți mesajul fără să verificați cine l-a trimis.

So:

• deschizi / verifici = informal singular
• deschideți / verificați = formal singular or plural

Yes. Both are correct.

• Nu ar trebui is the full form.
• N-ar trebui is the contracted form.

The contracted form is very common and natural. A learner should recognize both.

The structure is:

• N-ar trebui = you shouldn’t / it wouldn’t be advisable
• să deschizi mesajul = to open the message
• fără să verifici = without checking
• cine l-a trimis = who sent it

So the full structure is:

You shouldn’t open the message without checking who sent it.

Romanian word order here is quite natural and close to English, though the grammar inside the clauses is different.

A natural rhythm would group it like this:

N-ar trebui să deschizi mesajul / fără să verifici / cine l-a trimis.

A few pronunciation notes:

• N-ar sounds like the shortened nu ar
• să has a very short vowel
• l-a is pronounced together smoothly
• trimis is stressed on the second syllable: tri-MIS

Even if you do not produce every sound perfectly at first, keeping the sentence in these small chunks will help it sound more natural.