In the Custom backup scheme, you can set up a backup strategy in the way your enterprise needs it most: specify schedules for backups of each type and set up the retention rules.
The available backup types depend on the data type selected for backup: Microsoft Exchange Information Store, or Microsoft Exchange Mailboxes.
Microsoft Exchange Information Store
If you have selected Microsoft Exchange Information Store data type, the following backup types are available:
Specify on what schedule (Add schedule...) to perform a full database backup.
If a deduplicating vault is selected as a backup destination, full backups can be obtained by backing up only the changes that occurred since the last full backup. To do this, select the Create full backups using the Express full backup method check box. For more information on express backups, see "Express full backup method".
Specify on what schedule (Add schedule...) to perform a transaction log backup.
If the archive contains no full backups at the time of the task run, a full backup is created instead of the transaction log backup.
Microsoft Exchange Mailboxes
If you selected Microsoft Exchange Mailboxes data type, the following backup types are available:
Specify on what schedule (Add schedule...) to perform a full mailbox backup.
Specify on what schedule (Add schedule...) to perform an incremental mailbox backup.
If the archive contains no backups at the time of the task run, a full backup is created instead of the incremental backup.
Clean up archive
Specify how to get rid of old backups: either to apply retention rules regularly or clean up the archive during a backup when the destination location runs out of space.
By default, the retention rules are not specified. This means older backups will not be deleted automatically.
Note, in the Advanced settings of the Retention rules window for Exchange backups there is no option to consolidate a backup to be moved or deleted that has dependencies. The outdated backup (marked with the 
icon) will be kept until all backups that depend on it also become outdated. Then, all the chain will be deleted at once during the regular cleanup. If you chose moving outdated backups to the next location, the backup will be copied there without delay. Only its deletion from the current location is postponed.
Replication
[Optional] Specify whether to copy backups to another location. For more information about backup replication, see the "Setting up replication of backups" of the product help system or guides for Acronis Backup & Recovery 11.5.
When to validate
[Optional] Define when and how often to perform validation and whether to validate the entire archive or the latest backup in the archive.