Learn Hardcore French: Dans ce genre de travail, on communique principalement par courriel. - In this kind of job, people communicate mainly by email.

Dans is the normal preposition here because we are talking about being inside a particular context or setting (this kind of job / line of work).

dans ce genre de travail ≈ in this kind of work / in this line of work (within this environment)
en ce genre de travail is not idiomatic.

En works with:

fields, subjects: en médecine, en informatique
materials: en bois
some abstract situations: en difficulté, en vacances

With genre de + [noun], you use dans, not en.

Why is it ce genre de travail and not ce genre des travaux or ce genre du travail?

Genre de is a fixed pattern that introduces a type/kind of something:

ce genre de travail = this kind of work
The noun after de stays in the bare form, with no article:
- ce genre de musique
- ce genre de personne

So:

ce genre du travail is wrong here.
ce genre des travaux would mean something like this type of the works, which is not what we want.

You could say:

ce genre de travaux (plural) if you mean this kind of jobs/tasks/works in a more countable sense.
But the usual generic expression for “this kind of work” is ce genre de travail (singular, uncountable).

What exactly does on mean here, and why not nous?

On in modern French often means we, but it’s more general and more neutral:

on communique principalement par courriel
≈ people generally communicate mainly by email
≈ we generally communicate mainly by email (in this kind of job)

Reasons to use on:

It sounds more natural and less formal than nous in everyday speech.
It can mean people in general, not only the speaker’s group.

Using nous would be grammatically correct:

Nous communiquons principalement par courriel,
but it focuses more specifically on the speaker’s group, less on a general habit in that type of job.

If on often means we, why is the verb communique (3rd person singular) and not communiquons?

Grammatically, on is always third person singular, even when it means “we”:

on communique (never on communiquons)
on est contents
– verb: est (3rd singular)
– adjective: contents (often agrees in plural with the actual group)

So:

Verb agreement: on communique
Meaning in context: we / people in this kind of work communicate…

How is communiquer used here? Could you say se communiquer instead?

Here communiquer is used intransitively, with a preposition:

communiquer par courriel = communicate by email
Often you’ll see: communiquer avec quelqu’un par courriel
(communicate with someone by email)

Se communiquer exists but means something else (to pass something on to one another, or to spread):

La joie se communique facilement.
Joy spreads easily.

In this sentence, se communiquer would be wrong. You need communiquer on its own:
on communique principalement par courriel.

Why is principalement placed between on and communique? Could it go somewhere else?

Principalement is an adverb, and French often puts adverbs like this directly after the subject and before the verb:

on communique principalement par courriel

Other positions are possible and correct, but slightly change rhythm or emphasis:

On communique par courriel principalement.
(emphasis a bit more on by email as the main means)
Principalement, on communique par courriel.
(fronted for stylistic effect; more written or formal)

The original word order is the most neutral and common.

Why is it par courriel and not en courriel or par le courriel?

French uses par to express means or channel of communication:

par courriel – by email
par téléphone – by phone
par lettre – by letter
par fax – by fax

So:

en courriel is not idiomatic in this sense.
par le courriel would be understood, but adding le sounds less natural; for means of communication, French normally drops the article.

Hence: communiquer par courriel.

Can you say par courriels in the plural, or must it always be par courriel?

Both exist, but they’re used differently:

par courriel (singular)
– the usual, generic expression: by email as a means of communication.
par courriels (plural)
– emphasizes multiple individual messages:
Il m’a contacté par plusieurs courriels.
He contacted me through several emails.

In your sentence, we are talking about the general channel, so par courriel (singular) is the natural choice.

What’s the difference between courriel, email / e-mail, and mail in French?

Usage varies by region:

courriel
- Strongly used and promoted in Canada (especially Quebec).
- Understood everywhere in the francophone world.
- More “official”/standard in writing.
email / e-mail / mail
- Very common in France in everyday speech:
  Je t’enverrai un mail.
- Seen as more informal / English-influenced, but very widespread.

In a neutral written sentence like this one, courriel is perfectly correct and a bit more formal/standard.

Could we say Dans ce genre d’emploi instead of Dans ce genre de travail? Is there a difference?

You can say dans ce genre d’emploi, but there is a nuance:

travail – work in general; the nature of the work itself, what you actually do.
emploi – a job/position (more like a post in a company).
dans ce genre de travail
= in this kind of work / this kind of line of work (focus on the activity).
dans ce genre d’emploi
= in this kind of job/position (more about the type of job contract/post).

Both are possible; travail is slightly more general and common here.

Why is the present tense used (on communique) instead of something like on va communiquer?

The present tense in French is used, as in English, for general truths and habitual actions:

on communique principalement par courriel
= in this kind of work, people (typically) communicate mainly by email.

On va communiquer would mean we are going to communicate (future, specific situation), which is not the idea here. The sentence describes a general habit or usual practice, so the simple present is correct.

How do you pronounce dans ce genre de travail, on communique principalement par courriel? Are there any important liaisons?

Approximate pronunciation (standard French):

dans ce genre de travail → [dɑ̃ sə ʒɑ̃ʁ də tʁavaj]
on communique → [ɔ̃ kɔmynik]
principalement → [pʁɛ̃sipal(ə)mɑ̃] (the [ə] is often very weak or dropped)
par courriel → [paʁ kuʁjɛl]

Liaisons:

dans ce: no liaison (you don’t pronounce the s).
genre de travail: no obligatory liaison between these words either.
on communique: no liaison; just [ɔ̃] + [k].
par courriel: no liaison; par ends in a consonant and courriel starts with a consonant.