Source Deleted Users are not being deleted in the target environment.
Note: If AD Recycling Bin enabled, deleting objects is out of scope for DirSync.
This is not a product limitation. The AD environment tombstone policies dictate when object are removed from the Deleted Objects container, 14 days by default. The Recycling Bin will purge the objects based on their purge policy.
If you are noticing the users in the source are being deleted but they are not being deleted in the target you need to ensure that the following is in place.
Under your read workflow ensure that you have added the DELETE OBJECTS Workflow Step for your environments
Also for your source environment ensure that RECONCILE ON NEXT READ is selected.
