Each backup job is intended to collect mailbox data from an Exchange organization using Exchange Web Services and PowerShell and then place such data into the repository. Here is what happens when you run a backup job:
- At the initial execution of the backup job, the mailbox database file as well as other auxiliary files are going to be created in the corresponding subfolder, named <year_of_last_modification>. Veeam utilizes Extensible Storage Engine for Windows (ESE engine) to work with database files. The initial backup job execution creates the full backup of the whole mailbox content for selected mailboxes. All data during the job session is transferred using a backup proxy server. See Configuring Backup Proxies.
- At each subsequent execution of the backup job, all the information about the datastore structure and the mailbox data gets synchronized with the current state of the Exchange Organization using Exchange Web Services. Each successful job execution creates a new restore point that keeps the corresponding state of the mailbox datastore. These are incremental backups. Veeam detects modifications of the mailbox data (modified and/or new mailboxes) since the last backup job execution, and performs the incremental sync.
If you want to switch organization processing from one proxy to another, consider that after this new proxy assignment the organization backup job will perform the full sync with the Exchange server, that is, perform the full backup and create the whole datastore hierarchy in the repository from scratch. The full sync will also be applied when you target a backup job to another repository.