When you create a backup job, make sure to enable the application-aware image processing option, as described in the Specify Guest Processing Settings section of the Veeam Backup & Replication user guide.
By default, Exchange transaction logs will be truncated upon successful backup. To keep transaction logs for further processing by a third-party application, select the Exchange server VM from the list, click Edit and on the General tab select Perform copy only.
Support for Database Availability Groups (DAG)
Veeam Backup & Replication supports any configuration of DAGs. In particular, having all the databases active on a single node or with the active databases on each node. Transaction logs will be truncated on all DAG members.
For more information and recommendations, see the following articles: