Se minha sobrinha me mandar um e-mail, eu vou responder ainda na terça-feira à noite.

Because after se when you mean if in a real future situation, Portuguese normally uses the future subjunctive.

So:

• Se minha sobrinha me mandar um e-mail... = If my niece sends me an email...

For many regular -ar verbs, the future subjunctive form looks exactly like the infinitive:

• mandar → future subjunctive singular also mandar

That is why it may look like an infinitive, but here it is actually the correct finite verb form.

Compare:

• Se ela me manda e-mails todos os dias... = If she sends me emails every day... (habitual/present idea)
• Se ela me mandar um e-mail... = If she sends me an email... (future possibility)

Using mandará here would sound wrong after se in this kind of sentence.

Me means to me here.

So:

• mandar um e-mail = to send an email
• me mandar um e-mail = to send me an email

It is an object pronoun. In natural English, we usually say send me an email, not send an email to me, and Portuguese works similarly here.

A few more examples:

• Ela me ligou. = She called me.
• Ele me escreveu. = He wrote to me.
• Pode me mandar a foto? = Can you send me the photo?

In Brazilian Portuguese, placing me before the verb is very common and natural.

Eu vou responder is the very common spoken way to express the future in Brazilian Portuguese.

So these are both possible:

• eu vou responder
• eu responderei

But they are not equally common in everyday speech:

• eu vou responder = more natural and frequent in conversation
• eu responderei = more formal, more written, sometimes more emphatic

In Brazil, the ir + infinitive future is extremely common.

So:

• eu vou responder = I’m going to reply / I will reply

Here ainda adds the idea of still / already by then / as early as depending on context.

In this sentence, ainda na terça-feira à noite suggests something like:

• still on Tuesday night
• already on Tuesday night
• as early as Tuesday night

The exact best English wording depends on context, but the basic idea is that the reply will happen before Tuesday ends, specifically Tuesday night.

So ainda often adds a nuance of sooner than expected or before that time is over.

Examples:

• Vou terminar ainda hoje. = I’ll finish it today / I’ll still finish it today.
• Ela chega ainda esta semana. = She’ll arrive later this week / still this week.

Because they come from different contractions.

1. na terça-feira

This is:

• em + a terça-feira → na terça-feira

It means on Tuesday.

2. à noite

This is:

• a + a noite → à noite

This is a very common time expression meaning at night / in the evening / at night-time, depending on context.

So:

• na terça-feira = on Tuesday
• à noite = at night / in the evening

Together:

• na terça-feira à noite = on Tuesday night

That accent marks crase, which shows the contraction of two a sounds:

• the preposition a
• plus the feminine article a

So:

• a + a noite = à noite

This happens in many expressions with feminine nouns.

Examples:

• à noite = at night
• à tarde = in the afternoon
• à esquerda = to the left

It is not just a pronunciation mark; it shows a grammatical contraction.

Usually responder can be used directly with the thing being answered:

• responder um e-mail
• responder a pergunta
• responder a mensagem

In this sentence:

• eu vou responder means I’m going to reply / answer

The object the email is understood from the first clause, so it does not need to be repeated.

You could also say:

• eu vou responder o e-mail
• eu vou responder a ele depending on what exactly you want to repeat

For learners, the important point is that Portuguese often says:

• responder um e-mail

where English often prefers:

• reply to an email

So the structure does not match English exactly.

Yes. In Portuguese, subject pronouns are often omitted when the verb already makes the subject clear.

So both are possible:

• eu vou responder
• vou responder

Both mean I will reply.

Why include eu then?

Possible reasons:

• for emphasis
• for clarity
• because speakers often include pronouns in Brazilian Portuguese more than in European Portuguese
• simply because it sounds natural in that moment

So the sentence could also be:

• Se minha sobrinha me mandar um e-mail, vou responder ainda na terça-feira à noite.

That would still be perfectly natural.

Because um here means an / one, and the sentence refers to a single email, not email in general.

So:

• um e-mail = an email
• e-mail by itself can sound more general or less complete in this context

Compare:

• Se ela me mandar um e-mail... = If she sends me an email...
• Ela manda e-mail todo dia. = She sends email every day.

In the first sentence, one specific message is being imagined, so um is natural.

In Brazilian Portuguese, e-mail and email are both widely understood and used. Writing without the hyphen is also very common nowadays.

So all of these may appear:

• e-mail
• email

The playful spelling imeio exists, but it is informal, humorous, and nonstandard. It is not what you would normally use in careful writing.

Also, many Brazilians might simply say:

• mensagem
• mail in some contexts
• me manda um e-mail is still very normal and standard

Portuguese often uses mandar or enviar with e-mail.

Common options are:

• mandar um e-mail
• enviar um e-mail

Both mean to send an email.

There is also the verb emailar in some usage, but it is much less standard and much less common in careful language.

So for a learner, the safest natural choices are:

• mandar um e-mail
• enviar um e-mail

Terça-feira means Tuesday.

In Portuguese, weekdays from Monday to Friday traditionally use -feira:

• segunda-feira = Monday
• terça-feira = Tuesday
• quarta-feira = Wednesday
• quinta-feira = Thursday
• sexta-feira = Friday

In everyday speech, many Brazilians shorten them:

• terça
• quarta
• quinta

So na terça-feira and na terça can both be natural, depending on style and context.

Grammatically, se means if, not when.

However, in real-life context, if can sometimes sound very likely, so the idea may feel close to when in English. Still, the Portuguese sentence itself is using a conditional structure, not a time clause with quando.

Compare:

• Se minha sobrinha me mandar um e-mail... = If my niece sends me an email...
• Quando minha sobrinha me mandar um e-mail... = When my niece sends me an email...

Interestingly, both se and quando can be followed by the future subjunctive in Portuguese, but they express different meanings:

• se = condition
• quando = expected time/event

The sentence is quite natural as written, but Portuguese allows some flexibility.

Original:

• Se minha sobrinha me mandar um e-mail, eu vou responder ainda na terça-feira à noite.

Possible variations:

• Se minha sobrinha me mandar um e-mail, vou responder ainda na terça-feira à noite.
• Ainda na terça-feira à noite, eu vou responder, se minha sobrinha me mandar um e-mail.
• Se minha sobrinha me mandar um e-mail, eu ainda vou responder na terça-feira à noite.

Not every variation sounds equally neutral, but the basic meaning stays similar.

The original order is clear and very natural for learners to model.

Sobrinha normally means niece.

Related family words:

• sobrinho = nephew
• tia = aunt
• tio = uncle

So:

• minha sobrinha = my niece

There is no special hidden meaning here; it is just the normal family term.

Yes, minha means my, and it is the normal possessive adjective here:

• minha sobrinha = my niece

In Portuguese, possessives are used much like in English:

• meu irmão = my brother
• minha irmã = my sister

The form changes to match the gender and number of the noun:

• meu sobrinho = my nephew
• minha sobrinha = my niece
• meus sobrinhos = my nephews
• minhas sobrinhas = my nieces

Yes. Enviar works very well here.

So you could say:

• Se minha sobrinha me enviar um e-mail, eu vou responder ainda na terça-feira à noite.

Difference in tone:

• mandar = very common, everyday, natural
• enviar = also common, slightly more formal or neutral depending on context

Both are correct. In casual Brazilian Portuguese, mandar is extremely frequent.

A very natural casual version might be:

• Se minha sobrinha me mandar um e-mail, vou responder ainda na terça à noite.

Changes:

• omitted eu
• shortened terça-feira to terça

That sounds very normal in everyday Brazilian Portuguese.

You might also hear:

• Se minha sobrinha me mandar um email, vou responder ainda na terça à noite.

Same meaning, just with the modern spelling email.