diff --git a/src/requests/admin.cr b/src/requests/admin.cr
index 951c726..f1ddebe 100644
--- a/src/requests/admin.cr
+++ b/src/requests/admin.cr
@@ -1,4 +1,17 @@
 class DNSManager::Request
+	# Periodic actions to perform as an administrator.
+	IPC::JSON.message GetOrphanDomains, 6 do
+		def initialize()
+		end
+
+		def handle(dnsmanagerd : DNSManager::Service, event : IPC::Event) : IPC::JSON
+			user = dnsmanagerd.get_logged_user event
+			return Response::ErrorUserNotLogged.new unless user
+			dnsmanagerd.storage.get_orphan_domains dnsmanagerd.authd, user.uid
+		end
+	end
+	DNSManager.requests << GetOrphanDomains
+
 	# Periodic actions to perform as an administrator.
 	IPC::JSON.message Maintenance, 7 do
 		enum Subject
@@ -18,7 +31,6 @@ class DNSManager::Request
 		def handle(dnsmanagerd : DNSManager::Service, event : IPC::Event) : IPC::JSON
 			user = dnsmanagerd.get_logged_user event
 			return Response::ErrorUserNotLogged.new unless user
-
 			return Response::InsufficientRights.new unless user.admin
 
 			case @subject
diff --git a/src/responses/zone.cr b/src/responses/zone.cr
index a720834..8016546 100644
--- a/src/responses/zone.cr
+++ b/src/responses/zone.cr
@@ -110,5 +110,12 @@ class DNSManager::Response
 		end
 	end
 	DNSManager.responses << GeneratedZone
+
+	IPC::JSON.message OrphanDomainList, 24 do
+		property domains : Array(String)
+		def initialize(@domains)
+		end
+	end
+	DNSManager.responses << OrphanDomainList
 end
 
diff --git a/src/storage.cr b/src/storage.cr
index 7ccf25c..d09dd50 100644
--- a/src/storage.cr
+++ b/src/storage.cr
@@ -260,6 +260,29 @@ class DNSManager::Storage
 		Response::DomainDeleted.new domain
 	end
 
+	def get_orphan_domains(authd : AuthD::Client, user_id : UserDataID) : IPC::JSON
+		user_must_be_admin! user_id
+
+		Baguette::Log.warning "list all orphan domains (long computation)"
+		# Get all removed users from `authd`.
+		orphans = [] of String
+		user_data.each do |user|
+			begin
+				authd.get_user? user.uid
+			rescue e
+				Baguette::Log.warning "cannot get authd info on user #{user.uid}: #{e}"
+				Baguette::Log.warning "-> get his domains!"
+				# Verify the user still exists in `authd`.
+				user.domains.each do |domain|
+					orphans << domain
+				end
+			end
+		end
+		Baguette::Log.warning "total: #{orphans.size} orphans"
+
+		Response::OrphanDomainList.new orphans
+	end
+
 	def get_zone(user_id : UserDataID, domain : String) : IPC::JSON
 		user_data = user_must_exist! user_id
 		zone      = zone_must_exist! domain