Dobbiamo rimandare la riunione a domani mattina.

Dobbiamo is the we form of dovere, and it means we must or we have to.

Italian usually does not need the subject pronoun because the verb ending already shows who is doing the action:

• devo = I must
• devi = you must
• dobbiamo = we must

So noi is normally omitted unless you want emphasis or contrast:

• Noi dobbiamo rimandare la riunione = We have to postpone the meeting

Because dovere is a modal verb. In Italian, modal verbs such as:

• dovere = must / have to
• potere = can / to be able to
• volere = want

are followed directly by an infinitive.

So:

• dobbiamo rimandare = we have to postpone

There is no extra word like to in English, and no preposition such as di or a between the two verbs.

Yes, dobbiamo is present tense.

But Italian often uses the present tense for:

• current obligations
• plans
• near-future actions

Here the idea is:

• right now, we have the obligation/need
• the new meeting time is tomorrow morning

So the future meaning comes from a domani mattina, not from a future-tense verb.

Here rimandare means to postpone, to put off, or to reschedule for later.

In other contexts, rimandare can also mean other things, such as:

• to send back
• to refer back
• sometimes even to fail a student in a school context

But in this sentence, because it is followed by la riunione a domani mattina, the meaning is clearly postpone.

They are very close in meaning here.

Both can mean to postpone:

• Dobbiamo rimandare la riunione
• Dobbiamo rinviare la riunione

A useful rule:

• rimandare is very common and everyday
• rinviare can sound a bit more formal in some contexts

So for this sentence, both are possible, but rimandare is perfectly natural.

Because Italian normally needs an article before a noun in this kind of sentence.

• la riunione = the meeting
• una riunione = a meeting

Here the speakers are talking about a specific meeting, so la is used.

Saying just riunione here would sound incomplete or ungrammatical.

Because with rimandare, Italian often uses the pattern:

rimandare qualcosa a + new time/date

So:

• rimandare la riunione a domani mattina
• rimandare tutto a lunedì
• rimandare la decisione a più tardi

Here a introduces the new scheduled time.

In domani mattina is not correct Italian.

Per domani mattina can exist in Italian, but it usually gives a slightly different idea, more like for/by tomorrow morning depending on context.

After rimandare, the most natural construction is:

• rimandare ... a domani mattina

So this sentence uses the standard pattern.

In many sentences, yes:

• Ci vediamo domani mattina = We’ll see each other tomorrow morning
• Parto domani mattina = I’m leaving tomorrow morning

But with rimandare, a is very natural because it marks the new time the event is moved to:

• rimandare la riunione a domani mattina

So in this sentence, keeping a is the best choice.

Because domani mattina is a fixed time expression, like English tomorrow morning.

You do not say:

• la domani mattina

You simply say:

• domani mattina

It functions as an adverbial expression of time, not as an ordinary noun phrase.

The given order is the most neutral and natural:

• Dobbiamo rimandare la riunione a domani mattina.

Italian word order is somewhat flexible, but changes can add emphasis:

• La riunione dobbiamo rimandarla a domani mattina.
  This emphasizes the meeting.
• Dobbiamo rimandare a domani mattina la riunione.
  This is possible, but less neutral.

For a learner, the original version is the safest and most natural.

Yes.

You can say:

• Dobbiamo rimandarla a domani mattina.

Here la means it, referring to la riunione.

With modal verbs, Italian often allows two placements for the pronoun:

• La dobbiamo rimandare a domani mattina.
• Dobbiamo rimandarla a domani mattina.

Both are correct. The second one is often especially common in everyday speech.

Yes, but the meaning changes slightly.

• Dobbiamo rimandare... = we have to postpone...
• Bisogna rimandare... = it is necessary to postpone...

So bisogna is more impersonal. It does not directly say who has to do it, while dobbiamo clearly includes the speaker and other people in we.