Το συνημμένο που έστειλες άνοιξε αμέσως και φαινόταν καθαρά.

Το συνημμένο means the attachment (for example, an attached file in an email).

Literally, συνημμένο comes from a word meaning attached. In Greek, adjectives are often used as nouns when the noun is understood from context. So:

• συνημμένο = attached
• το συνημμένο = the attached thing → the attachment

It is neuter singular because the implied noun is something like αρχείο (file), which is neuter:

• το αρχείο
• το συνημμένο [αρχείο]

So even when αρχείο is left out, the adjective stays in the neuter form.

Here που means that / which and introduces a relative clause:

• Το συνημμένο που έστειλες
  = The attachment that you sent

This is very common Greek. Unlike English, Greek που does not change form depending on whether it means who, whom, that, or which. It is a very flexible relative word.

So:

• που έστειλες = that you sent

Because Greek verb endings often already show who the subject is.

• έστειλες = you sent (singular)

So Greek does not need an explicit εσύ (you) unless the speaker wants emphasis or contrast.

Compare:

• έστειλες = you sent
• εσύ έστειλες = you sent / you were the one who sent it

In this sentence, the subject you is understood from the verb ending.

Έστειλες is aorist, which is the normal past tense for a completed action.

So:

• έστειλες = you sent

It refers to a single completed event: the person sent the attachment.

This fits the sentence well because the speaker is referring to one finished action in the past.

Here άνοιξε means it opened.

The subject is το συνημμένο:

• Το συνημμένο ... άνοιξε
  = The attachment ... opened

In Greek, ανοίγω can work this way, just as in English:

• The door opened
• The file opened
• The attachment opened

So άνοιξε here is not necessarily saying who opened it; it simply describes what happened to the attachment/file.

This is one of the most useful things to notice in the sentence.

• άνοιξε = opened → aorist
• φαινόταν = was looking / appeared → imperfect

Greek often uses:

• aorist for a completed event
• imperfect for an ongoing state, background situation, or repeated/continuous action in the past

So the sentence presents:

1. The attachment opened immediately → one completed event
2. and it was appearing clearly / looked clear → the resulting state or ongoing appearance

This combination is very natural in Greek. English often uses simple past for both, but Greek distinguishes them more clearly.

Φαινόταν comes from φαίνομαι, which means things like:

• to appear
• to look
• to be visible
• to seem

In this sentence, it means something like:

• it looked clear
• it appeared clearly
• it was visible clearly

With a file or attachment, this usually means the contents displayed well and were easy to see/read.

Because καθαρά is an adverb here, not an adjective.

It describes how it appeared:

• φαινόταν καθαρά = it appeared clearly

Compare:

• καθαρός / καθαρή / καθαρό = clean / clear (adjective)
• καθαρά = clearly (adverb)

So:

• ένα καθαρό κείμενο = a clear text
• το κείμενο φαινόταν καθαρά = the text was visible clearly

This is very common in Greek: the neuter plural-looking form can function as an adverb.

The subject of both verbs is το συνημμένο.

So the sentence structure is:

• Το συνημμένο = subject
• που έστειλες = relative clause describing the subject
• άνοιξε αμέσως = first statement about the subject
• και φαινόταν καθαρά = second statement about the same subject

In other words:

• The attachment that you sent
  opened immediately
  and looked clear

Greek often does not repeat the subject when it stays the same.

Yes, word order in Greek is fairly flexible.

Here:

• άνοιξε αμέσως = opened immediately

This is a very natural order. But Greek could also say:

• άνοιξε το συνημμένο αμέσως in another context
• αμέσως άνοιξε for emphasis
• το συνημμένο άνοιξε αμέσως as here

The chosen order sounds neutral and natural.

So αμέσως is just modifying άνοιξε, and its position is flexible depending on emphasis and style.

It is mostly neutral, with a slightly email/workplace feel because of το συνημμένο.

• συνημμένο is a standard word for an email attachment
• The whole sentence sounds natural in messages, email replies, or workplace communication

It is not overly formal, but it is also not slangy.

Yes. A few natural alternatives are possible, depending on tone and exact meaning. For example:

• Το συνημμένο που έστειλες άνοιξε αμέσως και φαινόταν μια χαρά.
  = The attachment you sent opened immediately and looked fine.

• Το συνημμένο που έστειλες άνοιξε αμέσως και ήταν καθαρό.
  = The attachment you sent opened immediately and was clear.

• Το συνημμένο που έστειλες άνοιξε αμέσως και φαινόταν ευκρινώς.
  = ...and was clearly visible
  (more formal/literary)

But the original sentence is perfectly natural and idiomatic.

Yes, it can refer to either, depending on context.

It could mean:

• the document was easy to read
• the image showed up clearly
• the scanned file was visible without blur
• the attachment displayed properly

So καθαρά here is broad and practical: it means the content was clear/legible/visible.