Incremental Backup are very large

Hi.

Im using the option to create incremental backups every day and a full backup every week but the incremental backups are way to big to be incremental backups.

The full backup is 3,2 GB
The incremental backup is 1.5GB (about half a full).

So I got a incremental backups but it looks like the server creates a full backup of the email of de domains.
the manual clearly states:

• ...

Incremental Backup are very large