diff --git a/federationsender/queue/destinationqueue.go b/federationsender/queue/destinationqueue.go
index a9609361b..76357e83b 100644
--- a/federationsender/queue/destinationqueue.go
+++ b/federationsender/queue/destinationqueue.go
@@ -122,7 +122,8 @@ func (oq *destinationQueue) backgroundSend() {
 
 		// Retrieve any waiting things.
 		oq.runningMutex.RLock()
-		pendingPDUs, pendingEDUs := oq.pendingPDUs, oq.pendingEDUs
+		pendingPDUs, numPDUs := oq.pendingPDUs, len(oq.pendingPDUs)
+		pendingEDUs, numEDUs := oq.pendingEDUs, len(oq.pendingEDUs)
 		pendingInvites := oq.pendingInvites
 		idleCounter, sentCounter := oq.idleCounter.Load(), oq.statistics.SuccessCount()
 		oq.runningMutex.RUnlock()
@@ -156,13 +157,19 @@ func (oq *destinationQueue) backgroundSend() {
 				oq.runningMutex.Lock()
 				// Reallocate so that the underlying arrays can be GC'd, as
 				// opposed to growing forever.
+				for i := 0; i < numPDUs; i++ {
+					oq.pendingPDUs[i] = nil
+				}
+				for i := 0; i < numEDUs; i++ {
+					oq.pendingEDUs[i] = nil
+				}
 				oq.pendingPDUs = append(
 					[]*gomatrixserverlib.HeaderedEvent{},
-					oq.pendingPDUs[len(pendingPDUs):]...,
+					oq.pendingPDUs[numPDUs:]...,
 				)
 				oq.pendingEDUs = append(
 					[]*gomatrixserverlib.EDU{},
-					oq.pendingEDUs[len(pendingEDUs):]...,
+					oq.pendingEDUs[numEDUs:]...,
 				)
 				oq.runningMutex.Unlock()
 			}
@@ -179,7 +186,6 @@ func (oq *destinationQueue) backgroundSend() {
 					// the backoff has exceeded a maximum allowable value.
 					return
 				}
-				continue
 			} else if sent > 0 {
 				// If we successfully sent the invites then clear out
 				// the pending invites.
diff --git a/federationsender/queue/queue.go b/federationsender/queue/queue.go
index 74e6da3a9..031e9538c 100644
--- a/federationsender/queue/queue.go
+++ b/federationsender/queue/queue.go
@@ -21,6 +21,7 @@ import (
 	"github.com/matrix-org/dendrite/federationsender/producers"
 	"github.com/matrix-org/dendrite/federationsender/types"
 	"github.com/matrix-org/gomatrixserverlib"
+	"github.com/matrix-org/util"
 	log "github.com/sirupsen/logrus"
 )
 
@@ -189,13 +190,18 @@ func (oqs *OutgoingQueues) SendEDU(
 
 // filterDestinations removes our own server from the list of destinations.
 // Otherwise we could end up trying to talk to ourselves.
-func filterDestinations(origin gomatrixserverlib.ServerName, destinations []gomatrixserverlib.ServerName) []gomatrixserverlib.ServerName {
-	var result []gomatrixserverlib.ServerName
-	for _, destination := range destinations {
-		if destination == origin {
+func filterDestinations(origin gomatrixserverlib.ServerName, destinations []gomatrixserverlib.ServerName) (
+	result []gomatrixserverlib.ServerName,
+) {
+	strs := make([]string, len(destinations))
+	for i, d := range destinations {
+		strs[i] = string(d)
+	}
+	for _, destination := range util.UniqueStrings(strs) {
+		if gomatrixserverlib.ServerName(destination) == origin {
 			continue
 		}
-		result = append(result, destination)
+		result = append(result, gomatrixserverlib.ServerName(destination))
 	}
 	return result
 }