Hi! Veeam does this at a block level already, so only changed blocks are protected in subsequent job runs.

You may explain the environment a bit more to understand the used case.

When you talk about Windows in a vSphere VM, Veeam uses VMware Change Block Tracking (CBT). This works - as @MicoolPaul already said - at block level. So you don't have to worry about that in this situation. As far as I know this also works for Hpyer-V VMs. And also for Windows Agent backups - there is something similar to CBT. Veeam implemented Deduplication at Backup-File Level. 

Hi there,
I explain the case a little more.
I have a PC with an imap account in outlook, it receives emails daily, but not many, however the .ost file changes daily.
My question is, is there a way to configure Veeam to only copy changes on the file?
In the style of deduplication, or this should be done by the device where i make the copy.
Thank you for your attention.

I assume you use Veeam Windows Agent for this backup?

Here are the details for Windows Agent Changed Block Tracking (CBT):

https://helpcenter.veeam.com/docs/agentforwindows/userguide/backup_cbt_default.html?ver=40

In short: 

• When you use Volume-Backup: by using CBT, only changed blocks are backed up
• When you backup files, the whole file is backed up, when modification data has changed.

Thank you all,

Indeed, the copy would be made using an agent.

It is clear to me how Veeam works.

Thank you very much for your attention.

Greetings.

Wow!  That explains a lot.  IMO backing up changed blocks qualifies as an incremental backup, maybe even a very efficient incremental backup. 
But it’s a long way from what I would call deduplication.
With true deduplication:
if I had (3) copies of the exact same file, stored anywhere in the backup selection of a given Job, it would store one copy of the data, and two tiny pointers referencing the data for the other two filenames.
If I have (150) excel spreadsheets, all based off the same template, that when compared block for block are found to be 50% identical, those blocks would be deduplicated.
Thanks for clarifying.  So glad I’m only using the free windows agent.