Jag väntar med att svara på mejlet tills jag har läst allt noggrant.

In Swedish, vänta med att + infinitive means to wait before doing something or to put off doing something.

So:

• Jag väntar med att svara = I’m waiting before answering / I’m holding off on answering
• vänta att is not the normal pattern here

This is a very common structure:

• Hon väntar med att äta. = She is waiting before eating.
• Vi väntar med att bestämma oss. = We’re waiting before deciding.

So med att is part of the grammar pattern after vänta when you mean delaying an action.

Because after vänta med, Swedish normally uses att + infinitive.

Here:

• att svara = to answer

So the pattern is:

• vänta med att göra något = wait before doing something

Examples:

• Jag väntar med att ringa. = I’m waiting before calling.
• De väntar med att köpa huset. = They’re waiting before buying the house.

Even though English sometimes drops to in certain structures, Swedish keeps att here.

The verb svara often takes the preposition på when you answer something.

So:

• svara på mejlet = answer the email
• svara på en fråga = answer a question
• svara på brevet = answer the letter

This is just how the verb works in Swedish. A native English speaker may want to translate word for word and wonder why på is there, but it is simply part of the normal pattern with svara in many contexts.

Compare:

• Han svarade på min fråga.
• Jag måste svara på det här meddelandet.

Mejl is the common Swedish word for email, and mejlet is the definite singular form: the email.

Forms:

• ett mejl = an email
• mejlet = the email
• mejl = emails
• mejlen = the emails

So in this sentence, på mejlet means to the email / the email.

Swedish often adds the definite article as an ending, instead of using a separate word like the.

Tills means until.

In this sentence, it introduces the point in time when the waiting ends:

• Jag väntar ... tills jag har läst allt noggrant.
• I’ll wait ... until I have read everything carefully.

So the structure is:

• main clause + tills + subordinate clause

Examples:

• Jag stannar här tills du kommer. = I’ll stay here until you come.
• Vänta tills filmen börjar. = Wait until the movie starts.

Har läst is the present perfect tense in Swedish, formed with:

• har
  • supine form

Here:

• läsa = infinitive
• läser = present
• läste = past
• läst = supine/past participle form used with har in this tense

So:

• jag har läst = I have read

In this sentence, tills jag har läst allt noggrant means the person will wait up to the point when the reading is completed.

Using har läst emphasizes completion before answering.

Because tills starts a subordinate clause, and Swedish has special word order in subordinate clauses.

The normal order is:

• subject + sentence adverb + verb(s)

Here there is no sentence adverb, so we get:

• tills jag har läst allt noggrant

That is the normal structure.

A useful comparison:

• Main clause: Jag har läst allt.
• Subordinate clause: ... eftersom jag har läst allt.

If there were an adverb like inte, you would clearly see the subordinate clause pattern:

• ... tills jag inte har läst allt not
• ... tills jag har inte läst allt

So jag har läst is the correct order here.

Allt means everything / all of it.

In this sentence it refers to all the content of the email:

• läst allt noggrant = read everything carefully

This is the most natural and neutral choice.

Possible alternatives exist, but they have slightly different tone or emphasis:

• alltihop = all of it, the whole thing
• hela mejlet = the whole email

So you could say:

• ... tills jag har läst hela mejlet noggrant.

That would focus more directly on the whole email as a complete object.
Allt sounds very natural if you mean all the information/content.

Noggrant means carefully / thoroughly here.

It comes from the adjective noggrann:

• en noggrann person = a careful person
• noggrant = carefully / thoroughly

In this sentence, it functions as an adverb, describing how the reading is done:

• läst allt noggrant = read everything carefully

In Swedish, many adverbs are formed from the -t form of an adjective:

• snabb → snabbt
• tydlig → tydligt
• noggrann → noggrant

Yes, it is very natural.

It clearly means:

• I’m waiting before answering the email until...
• more idiomatically, I’m holding off on replying to the email until...

Swedish also has other natural ways to express something similar, for example:

• Jag svarar inte på mejlet förrän jag har läst allt noggrant.
  • Literally: I won’t answer the email until I have read everything carefully.

This version uses förrän, which is very common with negation:

• Jag gör det inte förrän i morgon. = I won’t do it until tomorrow.

Both are natural, but the original sentence focuses on waiting with answering, while the other focuses on not answering yet.

Yes, you could, but the tone changes a little.

• svara på mejlet = answer the email, reply to the email
• besvara mejlet = answer the email

Besvara is correct, but it can sound a bit more formal or written.
In everyday Swedish, svara på mejlet is usually more natural.

Examples:

• Jag måste svara på hennes mejl. = very natural everyday Swedish
• Vi kommer att besvara din förfrågan inom två dagar. = more formal/business style

So in your sentence, svara på mejlet is probably the best everyday choice.

Yes, but the style changes.

Common options:

• mejl = very common, modern everyday Swedish
• mail = also seen, but mejl is the more Swedish spelling
• epost or e-post = more formal or official

So you may see:

• på mejlet
• på e-postmeddelandet
• på e-posten

But in normal everyday language, mejlet is probably the most natural here.

Because Swedish usually expresses definiteness with an ending attached to the noun.

So:

• ett mejl = an email
• mejlet = the email

This is one of the biggest differences from English.
Instead of putting the before the noun, Swedish often adds a definite suffix.

More examples:

• en bok → boken
• ett hus → huset
• en fråga → frågan

So mejlet is completely normal Swedish grammar: the noun itself carries the meaning of the email.