Learn Hardcore Swahili: Barua yako itatumwa kesho asubuhi na karani wa posta. - Your letter will be sent tomorrow morning by the post clerk.

barua – letter
yako – your (singular “your”, agreeing with barua)
i-ta-tum-w-a (itatumwa / itatumwa) – it will be sent
- i- – subject marker for class 9/10 nouns (like barua)
- -ta- – future tense marker (“will”)
- -tum- – verb root “send”
- -w- – passive marker
- -a – final vowel
kesho – tomorrow
asubuhi – in the morning
na – by / with / and (here: by)
karani – clerk
wa – of (linking word in “clerk of the post office”)
posta – post office / postal service

So the basic structure is:
Letter your will-be-sent tomorrow morning by clerk of post-office.

Why is it barua yako and not yako barua for “your letter”?

In Swahili, possessives normally come after the noun they describe.

barua yako – your letter
kitabu changu – my book
rafiki wetu – our friend

Putting the possessive before the noun (yako barua) is ungrammatical.

So the pattern is:

[NOUN] + [POSSESSIVE]
barua + yako → barua yako (“your letter”)

How is the verb itatumwa (“will be sent”) formed, and why is it passive?

Itatumwa is a future passive verb form. Breakdown:

i- – subject marker for class 9/10 (barua is class 9)
-ta- – future tense (“will”)
-tum- – root “send”
-w- – passive marker
-a – final vowel

So:

kutuma – to send
atatuma barua – he/she will send the letter
barua itatumwa – the letter will be sent

The passive (itatumwa) focuses on the letter and the action happening to it, rather than on who is doing the sending. The agent (“by the postal clerk”) is added with na karani wa posta.

Why is the subject prefix i- in itatumwa, and not a- or something else?

Swahili verbs agree with the noun class of the subject. Barua belongs to noun class 9/10, whose subject marker is:

i- in the present and future (and some other tenses)

Examples:

barua inaongezeka – the mail is increasing
barua itafika kesho – the letter will arrive tomorrow
barua itatumwa – the letter will be sent

If the subject were a class 1 person (like mtu, “person”), you’d use a-:

mtu atatuma barua – a person will send the letter

But since barua is class 9, the verb must start with i-, not a-.

How would I say the same sentence in the active voice instead of passive?

Passive:

Barua yako itatumwa kesho asubuhi na karani wa posta.
– Your letter will be sent tomorrow morning by the postal clerk.

Active equivalent:

Karani wa posta atatuma barua yako kesho asubuhi.
- karani wa posta – postal clerk (subject)
- a-ta-tum-a – he/she will send
- barua yako – your letter
- kesho asubuhi – tomorrow morning

Difference in focus:

Passive: emphasizes the letter and the fact that it will be sent.
Active: emphasizes the clerk as the one doing the action.

What exactly is na doing in na karani wa posta? I thought na meant “and” or “with”.

Na is a very flexible word. Common meanings include:

and:
- chai na mkate – tea and bread
with:
- ninaenda na rafiki yangu – I am going with my friend
by (agent in passive constructions):
- Barua itatumwa na karani wa posta. – The letter will be sent by the postal clerk.

In this sentence it marks the agent (the doer) of the passive verb:

[Passive verb] + na + [doer]
itatumwa na karani wa posta – will be sent by the postal clerk

Can I change the order of kesho and asubuhi? For example, is asubuhi kesho also possible?

Both are used, but they sound slightly different:

kesho asubuhi – tomorrow morning (quite standard and common)
asubuhi kesho – literally “in the morning, tomorrow” (less common; can sound a bit more like clarification or emphasis)

In practice, for “tomorrow morning”, kesho asubuhi is the most natural choice.

About position in the sentence: time expressions are flexible:

Barua yako itatumwa kesho asubuhi na karani wa posta.
Kesho asubuhi barua yako itatumwa na karani wa posta.

Both are acceptable. Putting kesho asubuhi at the beginning can add a little emphasis on the time.

Why is it karani wa posta and not something like karani ya posta?

The link word wa is controlled by the noun class of the first noun in the “of” phrase.

karani – class 9 (borrowed noun; often behaves like class 9)
For many class 9 nouns, the associative “of” marker is wa

So:

karani wa posta – clerk of the post office
rafiki wa Juma – friend of Juma
barua ya Juma – Juma’s letter (here barua also takes ya; many 9/10 nouns can take ya or wa depending on usage and tradition)

The safest is to learn common collocations:

karani wa posta (fixed, normal phrase)
mwalimu wa shule – teacher of the school
dereva wa basi – driver of the bus

How would I say “Your letters will be sent tomorrow morning by the postal clerk” (plural “letters”)?

Make barua yako plural and adjust the verb agreement:

Subject noun stays barua, but now understood as plural (“letters”) – context gives plurality.
Possessive “your” (plural object) becomes zako to agree with class 10 plural.
Subject prefix in the verb becomes zi- for class 10.

Result:

Barua zako zitatumwa kesho asubuhi na karani wa posta.
- barua zako – your letters
- zi-ta-tum-w-a – they will be sent (class 10)

So the pattern:

singular: barua yako itatumwa
plural: barua zako zitatumwa

Are there other common verbs I could use instead of itatumwa to sound natural?

Yes, depending on nuance:

itapelekwa – it will be taken / delivered
- Barua yako itapelekwa kesho asubuhi na karani wa posta.
  Focuses on the act of physically taking the letter somewhere.
itawasilishwa – it will be delivered / submitted (more formal)
- Barua yako itawasilishwa kesho asubuhi.
itafikishwa – it will be made to arrive
- Barua yako itafikishwa kesho asubuhi.

Itatumwa is the neutral “will be sent”; itapelekwa is also very common in everyday speech.

Does this sentence sound formal, informal, or neutral? Would it be used in real life?

The sentence is neutral and natural. It’s exactly the kind of thing you might hear in or near a post office:

A clerk explaining what will happen to your letter.
Someone recounting information:
Walisema barua yako itatumwa kesho asubuhi na karani wa posta. – They said your letter will be sent tomorrow morning by the postal clerk.

It’s neither very formal nor slangy, so it’s safe to use in everyday conversation.