Kunden læser svarfristen i emailen.

In Danish, the definite article is often added to the end of the noun instead of appearing as a separate word.

• kunde = customer
• kunden = the customer

So -en here means the. The same pattern appears in svarfristen and emailen.

A separate word such as den is mainly used when there is an adjective before the noun, for example:

• den vigtige svarfrist = the important response deadline

Because Danish, like German, forms compound nouns very freely.

• svar = answer / reply
• frist = deadline / time limit
• svarfrist = response deadline
• svarfristen = the response deadline

English often writes similar ideas as two words, but Danish usually joins them into one compound noun.

Læser is the present tense of læse, meaning to read.

A useful point for English speakers: Danish verbs do not change for person the way English verbs sometimes do. So you get:

• jeg læser = I read / am reading
• du læser = you read / are reading
• kunden læser = the customer reads / is reading

The form stays the same.

The ending -en tells you these nouns are common gender nouns, the ones that normally take en in the indefinite form.

So here you have:

• en kunde → kunden
• en svarfrist → svarfristen
• en email / en e-mail → emailen / e-mailen

If a noun were neuter, it would usually take et in the indefinite form and -et in the definite singular.

Because the sentence is talking about specific, identifiable things:

• kunden = a particular customer
• svarfristen = a particular response deadline
• emailen = a particular email

If the sentence were introducing these as non-specific items, you would expect indefinite forms such as:

• en kunde
• en svarfrist
• en email

So the definite forms help show that the speaker has particular items in mind.

I usually means in or inside. With written communication, Danish often uses i for information contained within a text:

• i brevet = in the letter
• i rapporten = in the report
• i emailen = in the email

So the idea is that the response deadline is found within the content of the email.

This is a standard Danish main clause:

• Kunden = subject
• læser = finite verb
• svarfristen = object
• i emailen = prepositional phrase

So the pattern is basically:

Subject + verb + object + extra information

Danish is also a V2 language, which means the finite verb must be in the second position in a main clause. For example, if you move I emailen to the front, the verb still stays second:

• I emailen læser kunden svarfristen.

That sounds more marked, but it follows the normal Danish rule.

No. You may also see:

• e-mailen
• mailen

All of these are used. Email and e-mail are both common written forms, while mail is often more informal and very common in everyday speech.

So the spelling in your sentence is perfectly understandable, but it is not the only possible option.

In practice, most people will understand it as saying that the response deadline is found in the email, or that the customer reads that information in the email.

Grammatically, a phrase like i emailen can sometimes feel a little flexible in where it attaches, but context usually makes the meaning clear. If someone wanted to be extra explicit, they could rephrase the sentence, but as it stands, it is natural and understandable.