HOW DOES THIS WORK?
When you have this feature enabled in the dashboard, PieSync detects your deletions on one side of your sync and adds a tag/folder/list/group/...(app dependent) on the other side of the sync, named 'PieSync Trash'. You can then manually check this new subset of contacts, to see if you actually want to delete them there as well.
We choose not to automatically delete the deleted contacts on the other side, as we want to empower you, the end user, with taking the final decision on whether to delete the contacts forever, or to restore them. The 'PieSync Trash'...tag/folder/list/group/...(app dependent) allows you to do a double check before doing any unwanted damage with just a small manual action.
WHEN IS THIS AVAILABLE?
The availability of this feature is app and connection dependent. If the feature box (screenshots above) is not there to tick, it's simply not possible. We need to be able to detect deletions on one side and at the same time be able to create a tag/folder/list/group/...(app dependent) named 'PieSync Trash' on the other side. When available, we always explain how and in what direction this will work for that particular connection (see example above between Google Contacts and Podio).