oryu ttaemune meire cheombupaireul neohji moshaesseo.

때문에 means because of or due to.

So 오류 때문에 = because of an error / due to an error.

It is commonly attached to a noun:

• 비 때문에 = because of the rain
• 일 때문에 = because of work
• 오류 때문에 = because of an error

It often sounds a bit more formal or objective than some other cause expressions like -아서/어서.

In this sentence, 오류 때문에 tells you the reason the speaker could not attach the file.

Here, 에 marks the place or target that something is put into.

• 메일에 첨부파일을 넣다 = to put an attached file into an email

So:

• 메일에 = into the email
• 첨부파일을 = the attached file
• 넣다 = to put in

If you used 메일을, that would make mail/email the direct object, which does not fit this verb as naturally here.

You can think of the structure as:

[place/container]에 [object]을/를 넣다
= put [object] into [place/container]

Examples:

• 가방에 책을 넣었어. = I put a book in the bag.
• 메일에 첨부파일을 넣었어. = I put an attached file in the email.

Both ideas are possible, but they are slightly different in feel.

• 첨부파일을 넣다 literally means to put an attached file into the email
• 파일을 첨부하다 means to attach a file

In real usage, Koreans often say both kinds of expressions, especially in computer/email contexts.

Compare:

• 메일에 첨부파일을 넣지 못했어.
• 메일에 파일을 첨부하지 못했어.

The second one may sound a little more directly like I couldn’t attach the file, while the original sentence feels a bit like I couldn’t put the attachment into the email. The meaning is very close.

넣지 못했어 means couldn’t put in or wasn’t able to put in.

Breakdown:

• 넣다 = to put in
• -지 못하다 = cannot do / fail to do
• 못했어 = couldn’t do it / was unable to do it

So:

• 넣지 못했어 = was unable to put it in

This expresses inability, not just choice.

That matters because:

• 안 넣었어 = I didn’t put it in (maybe I chose not to)
• 못 넣었어 / 넣지 못했어 = I couldn’t put it in (something prevented me)

Since the sentence says 오류 때문에, the inability reading makes perfect sense.

They are very similar, and both mean couldn’t put it in.

• 못 넣었어
• 넣지 못했어

In everyday speech, 못 + verb is very common and often feels a bit more conversational and direct.

-지 못하다 can sound slightly more formal, careful, or written, though in many situations the difference is small.

So this sentence could also be said as:

• 오류 때문에 메일에 첨부파일을 못 넣었어.

That would sound very natural too.

Korean often leaves out the subject when it is obvious from context.

So 오류 때문에 메일에 첨부파일을 넣지 못했어 naturally implies:

• I couldn’t attach the file to the email because of an error

But depending on context, it could also mean:

• we couldn’t
• he/she couldn’t
• they couldn’t

In conversation, Korean does not always state pronouns like I, you, or he/she unless needed for clarity.

If you wanted to make the subject explicit, you could say:

• 제가 오류 때문에 메일에 첨부파일을 넣지 못했어요. = I couldn’t attach the file to the email because of an error.

-했어 is the informal, casual past tense ending.

Here:

• 못했다 = could not do
• 못했어 = casual spoken form of couldn’t do

So the sentence is in a casual style, probably used with a friend, coworker you are close to, or in relaxed conversation.

More polite versions would be:

• 오류 때문에 메일에 첨부파일을 넣지 못했어요.
• 오류 때문에 메일에 첨부파일을 첨부하지 못했어요.

Very formal/written:

• 오류 때문에 메일에 첨부파일을 넣지 못했습니다.

오류 means error in general, and it is very commonly used for system, software, or technical errors.

In this sentence, because the context is email and attachments, most learners would understand it as something like:

• a system error
• a software error
• a technical glitch

In daily speech, some people also say 에러 from English error, especially in tech contexts.

So you may hear both:

• 오류가 났어.
• 에러가 났어.

Both can mean There was an error.

첨부파일을 is the direct object of 넣다.

• 첨부파일 = attached file / attachment
• 을 = object marker

The thing being put into the email is the attachment, so it gets 을/를.

Structure:

• 메일에 = into the email
• 첨부파일을 = the attachment
• 넣지 못했어 = couldn’t put in

This is a very common Korean pattern:

• 상자에 선물을 넣었어. = I put a gift in the box.
• 이메일에 사진을 넣었어. = I put a photo in the email.

Usually, yes.

Because of 못했어 plus 오류 때문에, the sentence strongly suggests that the speaker was unable to do it due to an outside problem.

It sounds like:

• the speaker intended to attach the file
• something prevented it
• the reason was an error

So it is different from simply saying:

• 첨부파일을 안 넣었어. = I didn’t put in the attachment

That version does not necessarily imply any attempted action or obstacle.

Yes. Even though the Korean literally uses put in (넣다), a natural English translation is often:

• I couldn’t attach the file to the email because of an error.

That is usually the best English phrasing.

A more literal translation would be:

• Because of an error, I couldn’t put the attached file into the email.

But in normal English, attach the file sounds much more natural than put the attached file into the email.