diff --git a/roomserver/api/output.go b/roomserver/api/output.go
index b25353ae4..d6c09f9e8 100644
--- a/roomserver/api/output.go
+++ b/roomserver/api/output.go
@@ -29,6 +29,22 @@ const (
 	// OutputTypeRetireInviteEvent indicates that the event is an OutputRetireInviteEvent
 	OutputTypeRetireInviteEvent OutputType = "retire_invite_event"
 	// OutputTypeRedactedEvent indicates that the event is an OutputRedactedEvent
+	//
+	// This event is emitted when a redaction has been 'validated' (meaning both the redaction and the event to redact are known).
+	// Redaction validation happens when the roomserver receives either:
+	// - A redaction for which we have the event to redact.
+	// - Any event for which we have a redaction.
+	// When the roomserver receives an event, it will check against the redactions table to see if there is a matching redaction
+	// for the event. If there is, it will mark the redaction as validated and emit this event. In the common case of a redaction
+	// happening after receiving the event to redact, the roomserver will emit a OutputTypeNewRoomEvent of m.room.redaction
+	// immediately followed by a OutputTypeRedactedEvent. In the uncommon case of receiving the redaction BEFORE the event to redact,
+	// the roomserver will emit a OutputTypeNewRoomEvent of the event to redact immediately followed by a OutputTypeRedactedEvent.
+	//
+	// In order to honour redactions correctly, downstream components must ignore m.room.redaction events emitted via OutputTypeNewRoomEvent.
+	// When downstream components receive an OutputTypeRedactedEvent they must:
+	// - Pull out the event to redact from the database. They should have this because the redaction is validated.
+	// - Redact the event and set the corresponding `unsigned` fields to indicate it as redacted.
+	// - Replace the event in the database.
 	OutputTypeRedactedEvent OutputType = "redacted_event"
 )
 
diff --git a/roomserver/storage/shared/storage.go b/roomserver/storage/shared/storage.go
index a9cb57821..e2e5daf95 100644
--- a/roomserver/storage/shared/storage.go
+++ b/roomserver/storage/shared/storage.go
@@ -563,6 +563,10 @@ func (d *Database) handleRedactions(
 		// we've seen this redaction before or there is nothing to redact
 		return nil, "", nil
 	}
+	if redactedEvent.RoomID() != redactionEvent.RoomID() {
+		// redactions across rooms aren't allowed
+		return nil, "", nil
+	}
 
 	// mark the event as redacted
 	err = redactedEvent.SetUnsignedField("redacted_because", redactionEvent)
diff --git a/syncapi/consumers/roomserver.go b/syncapi/consumers/roomserver.go
index ba2b2055b..c65027168 100644
--- a/syncapi/consumers/roomserver.go
+++ b/syncapi/consumers/roomserver.go
@@ -83,8 +83,13 @@ func (s *OutputRoomEventConsumer) onMessage(msg *sarama.ConsumerMessage) error {
 	case api.OutputTypeNewRoomEvent:
 		// Ignore redaction events. We will add them to the database when they are
 		// validated (when we receive OutputTypeRedactedEvent)
-		if output.NewRoomEvent.Event.Type() == gomatrixserverlib.MRoomRedaction && output.NewRoomEvent.Event.StateKey() == nil {
-			return nil
+		event := output.NewRoomEvent.Event
+		if event.Type() == gomatrixserverlib.MRoomRedaction && event.StateKey() == nil {
+			// in the special case where the event redacts itself, just pass the message through because
+			// we will never see the other part of the pair
+			if event.Redacts() != event.EventID() {
+				return nil
+			}
 		}
 		return s.onNewRoomEvent(context.TODO(), *output.NewRoomEvent)
 	case api.OutputTypeNewInviteEvent:
diff --git a/sytest-whitelist b/sytest-whitelist
index 30380af0e..0628ea26e 100644
--- a/sytest-whitelist
+++ b/sytest-whitelist
@@ -160,14 +160,6 @@ User can create and send/receive messages in a room with version 1
 POST /createRoom ignores attempts to set the room version via creation_content
 Inbound federation rejects remote attempts to join local users to rooms
 Inbound federation rejects remote attempts to kick local users to rooms
-# SyTest currently only implements the v1 endpoints for /send_join and /send_leave,
-# whereas Dendrite only supports the v2 endpoints for those, so let's ignore this
-# test for now.
-#An event which redacts itself should be ignored
-# SyTest currently only implements the v1 endpoints for /send_join and /send_leave,
-# whereas Dendrite only supports the v2 endpoints for those, so let's ignore this
-# test for now.
-#A pair of events which redact each other should be ignored
 Full state sync includes joined rooms
 A message sent after an initial sync appears in the timeline of an incremental sync.
 Can add tag
@@ -295,6 +287,14 @@ POST /rooms/:room_id/redact/:event_id as random user does not redact message
 POST /redact disallows redaction of event in different room
 An event which redacts itself should be ignored
 A pair of events which redact each other should be ignored
+Redaction of a redaction redacts the redaction reason
+An event which redacts an event in a different room should be ignored
+Can receive redactions from regular users over federation in room version 1
+Can receive redactions from regular users over federation in room version 2
+Can receive redactions from regular users over federation in room version 3
+Can receive redactions from regular users over federation in room version 4
+Can receive redactions from regular users over federation in room version 5
+Can receive redactions from regular users over federation in room version 6
 Outbound federation can backfill events
 Inbound federation can backfill events
 Backfill checks the events requested belong to the room