Ten plik jest mały, ale załącznik w twoim mailu był za duży.

Because plik is a masculine singular noun in Polish, and ten is the demonstrative adjective that matches masculine singular nouns.

Polish this changes depending on gender:

• ten = masculine
• ta = feminine
• to = neuter

So:

• ten plik = this file
• ta wiadomość = this message
• to zdjęcie = this photo

The adjective/determiner has to agree with the noun’s gender, number, and case.

Because the sentence contrasts a present situation with a past situation.

• jest = is (present tense)
• był = was (past tense, masculine singular)

So the sentence is saying:

• This file is small now
• but the attachment in your email was too big

The form był agrees with załącznik, which is masculine singular.

Related past tense forms are:

• był = he/it was (masculine)
• była = she/it was (feminine)
• było = it was (neuter)
• byli / były = they were

Because both adjectives describe masculine singular nouns:

• plik → masculine singular
• załącznik → masculine singular

So the adjective form is:

• mały = small
• duży = big/large

Examples with other genders:

• mała wiadomość = a small message
• duże zdjęcie = a large photo

In this sentence, the adjectives appear after jest and był, but they still agree with the noun they describe.

Duży means big/large, but za duży means too big / too large.

The word za in this kind of phrase means too:

• za duży = too big
• za mały = too small
• za drogi = too expensive
• za późno = too late

So:

• był duży = it was big
• był za duży = it was too big

That small word za is very important here because it adds the idea that the size was a problem.

Because the preposition w here means in, and after w Polish usually requires the locative case when talking about location.

So:

• basic form: twój mail
• after w: w twoim mailu

Both the possessive word and the noun change:

• twój → twoim
• mail → mailu

This is one of the most important things to get used to in Polish: prepositions often force case changes.

Because after w meaning in, the noun goes into the locative singular.

So:

• nominative: mail
• locative: mailu

That is why you get:

• w mailu = in the email

This pattern is common with many masculine nouns:

• dom → w domu
• sklep → w sklepie
• pliku would be the locative of plik, as in w pliku

With mail, learners should also know that spelling varies. You may see:

• mail
• e-mail

And in speech, mail is very common.

Because twoim is the correct locative singular masculine/neuter form of twój after w.

Here are some forms of twój:

• twój = your (masculine nominative)
• twoja = your (feminine nominative)
• twoje = your (neuter nominative / plural non-masculine personal in some contexts)
• twoim = your (locative/instrumental masculine or neuter singular)

So:

• twój mail = your email
• w twoim mailu = in your email

Twym is a more literary/poetic short form of twoim, not the normal everyday choice here.

They are related, but not identical.

• plik = file
• załącznik = attachment

A plik is any file in general. A załącznik is specifically something attached, for example to an email.

So in this sentence:

• Ten plik jest mały = This file is small
• ale załącznik w twoim mailu był za duży = but the attachment in your email was too large

An attachment is usually a file, but not every file is an attachment.

Because Polish does not have articles like a/an/the.

English says:

• the file
• an attachment

Polish usually just uses the noun without an article:

• plik
• załącznik

If Polish wants to be more specific, it often uses words like:

• ten = this
• tamten = that

So ten plik helps make the meaning more specific, similar to this file.

Yes, you could, but it would change the meaning slightly.

• jest za duży = is too large (present)
• był za duży = was too large (past)

Use jest if the attachment is still being discussed as a current problem. Use był if you are referring to the email/attachment as something from an earlier moment.

So both are grammatically fine, but they express different time references.

Yes, in this sentence ale means but.

It connects two contrasting ideas:

• Ten plik jest mały
• ale
• załącznik w twoim mailu był za duży

So the contrast is:

• this file is small
• but that attachment was too big

In everyday Polish, ale is the most common and natural word for this kind of contrast.

Mail is very common in everyday Polish, especially in speech and informal writing.

However, more formal alternatives exist, such as:

• e-mail
• wiadomość e-mail
• wiadomość

So:

• w twoim mailu = natural and common
• w twojej wiadomości e-mail = more formal/full

A learner should recognize that mail is widely used and completely normal in many situations.

Yes. Plik jest mały is grammatically correct and means The file is small or A file is small, depending on context.

Adding ten makes it more specific:

• Plik jest mały = The file is small / A file is small
• Ten plik jest mały = This file is small

So ten is not required for grammar, but it helps point to a specific file.

A rough pronunciation is:

za-WONCH-neek

More carefully:

• za = like za
• łącz contains ą, which is a nasal vowel; before cz it sounds close to on
• nik = neek

So załącznik is approximately:

za-WON-chnik or za-WONCH-neek

The exact Polish sound is not identical to any single English vowel, but thinking of ą here as something like on is a useful approximation for learners.

Yes, literally w twoim mailu means in your email, so it can refer to something contained in the email.

However, because the noun is załącznik (attachment), the meaning is naturally understood as:

• the attachment in/with your email

If you wanted to be extra explicit, you could also say something like:

• załącznik do twojego maila = the attachment to your email

But the original sentence sounds natural and clear.