Toplantı saati netleşince size e-posta göndereceğim.

-ince/-ınca/-ünce/-unca is a suffix that usually means when, once, or after.

So netleşince means when it becomes clear/finalized.
It turns the verb into a time clause:

• Toplantı saati netleşince... = When the meeting time is finalized...

The exact form -ince is chosen here because of vowel harmony.

It is built in steps:

• net = clear
• netleşmek = to become clear / to get finalized
• netleş-
  • -ince = netleşince = when it becomes clear

The part -leşmek is a useful pattern in Turkish. It often means to become X:

• temiz = clean → temizleşmek = to become clean
• zor = difficult → zorlaşmak = to become difficult
• net = clear → netleşmek = to become clear

This is a very common Turkish noun-compound pattern.

• toplantı = meeting
• saati = its time / time

Together, toplantı saati means meeting time.

The -i on saati is the 3rd-person possessive suffix, which is often used in noun compounds. In this kind of structure, it does not literally mean his/her. It is just part of the normal pattern.

Compare:

• ders saati = class time
• yemek saati = mealtime
• otobüs durağı = bus stop

Toplantı saati is the more natural, compact way to say meeting time.

Toplantının saati is also possible, but it sounds more explicitly like the time of the meeting, often with a slightly more specific or contrastive feel.

So:

• toplantı saati = meeting time
• toplantının saati = the time of the meeting

In everyday Turkish, the shorter compound toplantı saati is very common.

Size is the dative form of siz:

• siz = you (plural or polite singular)
• size = to you

With göndermek (to send), the person receiving something is usually marked with the dative:

• size e-posta göndermek = to send an email to you

Sizi would be the direct-object form (you), which does not fit here.

Also, siz/size can mean:

• you all
• you in a polite/formal singular sense

Göndereceğim means I will send.

It can be broken down like this:

• gönder- = send
• -ecek = future tense
• -im = 1st person singular

So the underlying structure is roughly:

• gönder-ecek-im

In the actual spoken/written form, the k softens before the following vowel, giving:

• göndereceğim

So the whole verb already includes the idea of I.

Because Turkish often leaves subject pronouns out when the verb already shows the person.

Here, göndereceğim already means I will send, so ben is not necessary.

You could say:

• Ben size e-posta göndereceğim.

But that would sound more emphatic, like:

• I will send you an email.

Without ben, the sentence is more neutral and natural.

Because the object is indefinite here.

• e-posta göndereceğim = I will send an email
• e-postayı göndereceğim = I will send the email

In Turkish, a specific/definite direct object usually takes the accusative ending.
An indefinite one often does not.

So this sentence suggests an email in a general sense, not a particular email already known to both speakers.

That is the normal Turkish sentence pattern. Turkish often prefers verb-final word order.

This sentence is structured like this:

• Toplantı saati netleşince = when the meeting time is finalized
• size = to you
• e-posta = an email
• göndereceğim = I will send

So the main verb naturally comes at the end.

English speakers often want to place the verb earlier, but in Turkish, verb-final order is usually the most natural choice.

Yes, that is also natural.

There is a small nuance:

• netleşince = when it becomes clear/finalized; often used when plans are still being settled
• belli olunca = when it becomes known/apparent

Both work well here.
Netleşince feels especially good for schedules, plans, arrangements, and details that are not fully settled yet.

Yes, you could.

Both are grammatical, but they feel a little different:

• netleşince = when/once it becomes finalized
• netleştiğinde = when it has become finalized / when it is finalized

In many everyday situations, netleşince sounds more natural and conversational.
Netleştiğinde can sound a bit more formal or slightly more neutral depending on context.

So the original sentence is a very natural everyday choice.