لن يفتح صديقي رابطا مشبوها أبدا.

لن is a future negation particle. It means will not.

So:

لن يفتح = he will not open

In this sentence, it tells you the action is negated in the future.

After لن, Arabic uses the imperfect verb in the subjunctive.

The fully vowelled form here is:

يَفْتَحَ not يَفْتَحُ

But in normal unvowelled writing, both are written the same way:

يفتح

So the spelling does not change, but the grammar does.

Because لا and لن do different jobs.

• لا يفتح often means he does not open / he is not opening / he doesn’t open
• لن يفتح means he will not open

So لن is the correct choice when the meaning is specifically future.

Arabic often uses verb–subject–object order in verbal sentences.

So:

لن يفتح صديقي رابطا مشبوها أبدا

is a normal verbal sentence:
will-not open my-friend a-link suspicious ever

You can also say:

صديقي لن يفتح رابطا مشبوها أبدا

That is also correct, but it gives a bit more emphasis to my friend as the topic.

صديق means friend.

Add the suffix ـي meaning my, and you get:

صديقي = my friend

So this is a possessed noun:

• صديق = friend
• صديقي = my friend

Because it is possessed, it is automatically definite.

In Arabic, the subject of a verbal sentence often comes after the verb.

So in:

لن يفتح صديقي...

the verb is يفتح = open
and the doer of the action is صديقي = my friend

That makes صديقي the subject.

رابطا is the direct object of the verb, so it is in the accusative case.

The fully vowelled form is:

رَابِطًا

It is accusative because it is the thing being opened:
open what? → a link

It is also indefinite, meaning a link, not the link.

That is why it has tanwīn fatḥ in the fully vocalized form.

Because the sentence means a suspicious link, not the suspicious link.

In Arabic:

• رابط مشبوه = a suspicious link
• الرابط المشبوه = the suspicious link

So the lack of ال shows the phrase is indefinite.

Because مشبوه is an adjective describing رابط.

In Arabic, adjectives agree with the nouns they describe in:

• definiteness
• gender
• number
• case

Since رابطا is:

• masculine
• singular
• indefinite
• accusative

the adjective must match it:

مشبوها
fully vowelled: مَشْبُوهًا

مشبوه means suspicious or suspect.

So:

رابط مشبوه = a suspicious link

This is a very natural phrase in Modern Standard Arabic, especially in internet or security contexts.

أبدا means ever or never at all, depending on the sentence.

In a negative sentence like this one, it gives the meaning never:

لن يفتح... أبدا = will never open...

Without أبدا, the sentence would still mean will not open, but أبدا makes the negation stronger and more absolute.

Yes, very natural.

Arabic often uses أبدا with a negative expression to mean never:

• لن أفعل ذلك أبدا = I will never do that
• لا أنساه أبدا = I never forget it / I will never forget it

So لن يفتح صديقي رابطا مشبوها أبدا is completely natural.

Fully vowelled, it is:

لَنْ يَفْتَحَ صَدِيقِي رَابِطًا مَشْبُوهًا أَبَدًا

A helpful pronunciation is:

lan yaftaḥa ṣadīqī rābiṭan mashbūhan abadan

That corresponds to:
My friend will never open a suspicious link.