Se non trovi il messaggio, controlla la cartella spam.

Se means if. It introduces a condition:

• Se non trovi il messaggio = If you don’t find the message

So the sentence has the structure if X, do Y:

• Se non trovi il messaggio, controlla la cartella spam.
• If you don’t find the message, check the spam folder.

Non is the standard way to make a verb negative in Italian. It goes directly before the verb:

• trovi = you find
• non trovi = you do not / don’t find

So:

• Se trovi il messaggio = If you find the message
• Se non trovi il messaggio = If you don’t find the message

Because trovi is the tu form of trovare in the present indicative:

• io trovo
• tu trovi
• lui/lei trova

Here the sentence is talking to you informally, even though tu is not written:

• (tu) trovi = you find

So Se non trovi... means If you don’t find...

Italian often leaves out subject pronouns when they are clear from the verb form. This is very common.

So instead of saying:

• Se tu non trovi il messaggio...

Italian normally says:

• Se non trovi il messaggio...

The verb trovi already tells you the subject is tu.

Controlla is the informal singular imperative of controllare, meaning check.

So:

• controlla! = check!

This matches the person being addressed in trovi:

• Se non trovi... = If you don’t find...
• controlla... = check...

So the sentence is giving an instruction to one person informally.

That is normal for many -are verbs in Italian.

For controllare:

• tu controlli = you check
• lui/lei controlla = he/she checks
• controlla! = check! (informal singular command)

So the tu imperative of many -are verbs looks the same as the lui/lei present form.

Examples:

• parla! = speak!
• ascolta! = listen!
• controlla! = check!

Italian uses articles more often than English does. In this sentence, the speaker is referring to specific things in context:

• il messaggio = the message
• la cartella spam = the spam folder

Even when English might sometimes sound fine without an article in a short instruction, Italian usually keeps it.

It means spam folder.

• cartella = folder
• spam = spam

In Italian tech language, English words are often kept, so spam is very common.
You may also hear more explicit alternatives such as:

• cartella della posta indesiderata
• posta indesiderata

But cartella spam is very natural and common.

Because controllare can take a direct object:

• controlla la cartella spam = check the spam folder

This is like saying:

• check the folder

If you said controlla nella cartella spam, that would sound more like check in the spam folder, which shifts the structure a bit. It is possible in some contexts, but here controlla la cartella spam is the most straightforward and natural instruction.

Italian commonly uses the present indicative after se for a real, possible condition in the present or near future.

So:

• Se non trovi il messaggio... literally uses the present tense, but in English it naturally corresponds to:
• If you don’t find the message...

This is normal Italian usage. You do not need a future here.

The comma is natural and standard here because the sentence begins with the if-clause:

• Se non trovi il messaggio, controlla la cartella spam.

The comma helps separate the condition from the main instruction.
In short messages or informal writing, people may sometimes omit punctuation, but with the sentence written this way, the comma is the normal choice.

Yes. The sentence as written is informal singular, used with tu.

A formal version would be:

• Se non trova il messaggio, controlli la cartella spam.

Here:

• trova = formal you find
• controlli = formal command check

So the original sentence is what you would say to a friend, colleague you address with tu, or in a casual instruction.

Yes, depending on nuance.

Possible alternatives:

• guarda la cartella spam = look in / check the spam folder
• verifica la cartella spam = check/verify the spam folder
• dai un’occhiata alla cartella spam = take a look at the spam folder

But controlla la cartella spam is a very standard, clear instruction, especially in tech or customer-support style language.