diff --git a/pkg/kncloudevents/message_sender.go b/pkg/kncloudevents/message_sender.go
index b9fc4f70f15..1a425cd601b 100644
--- a/pkg/kncloudevents/message_sender.go
+++ b/pkg/kncloudevents/message_sender.go
@@ -150,6 +150,8 @@ func RetryConfigFromDeliverySpec(spec duckv1.DeliverySpec) (RetryConfig, error)
 
 	retryConfig := NoRetries()
 
+	retryConfig.CheckRetry = checkRetry
+
 	if spec.Retry != nil {
 		retryConfig.RetryMax = int(*spec.Retry)
 	}
@@ -176,3 +178,7 @@ func RetryConfigFromDeliverySpec(spec duckv1.DeliverySpec) (RetryConfig, error)
 
 	return retryConfig, nil
 }
+
+func checkRetry(_ context.Context, resp *nethttp.Response, _ error) (bool, error) {
+	return resp != nil && resp.StatusCode >= 300, nil
+}
diff --git a/pkg/kncloudevents/message_sender_test.go b/pkg/kncloudevents/message_sender_test.go
index aa6e4545b62..a6793c44823 100644
--- a/pkg/kncloudevents/message_sender_test.go
+++ b/pkg/kncloudevents/message_sender_test.go
@@ -17,11 +17,18 @@ limitations under the License.
 package kncloudevents
 
 import (
+	"context"
+	nethttp "net/http"
+	"net/http/httptest"
+	"sync"
 	"testing"
 	"time"
 
 	"github.com/stretchr/testify/assert"
+	"k8s.io/utils/pointer"
+
 	duckv1 "knative.dev/eventing/pkg/apis/duck/v1"
+	eventingduck "knative.dev/eventing/pkg/apis/duck/v1"
 )
 
 // Test The RetryConfigFromDeliverySpec() Functionality
@@ -120,3 +127,150 @@ func TestRetryConfigFromDeliverySpec(t *testing.T) {
 		})
 	}
 }
+
+func TestHttpMessageSenderSendWithRetries(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name         string
+		config       *RetryConfig
+		wantStatus   int
+		wantDispatch int
+		wantErr      bool
+	}{
+		{
+			name: "5 max retry",
+			config: &RetryConfig{
+				RetryMax: 5,
+				CheckRetry: func(ctx context.Context, resp *nethttp.Response, err error) (bool, error) {
+					return true, nil
+				},
+				Backoff: func(attemptNum int, resp *nethttp.Response) time.Duration {
+					return time.Millisecond
+				},
+			},
+			wantStatus:   nethttp.StatusServiceUnavailable,
+			wantDispatch: 6,
+			wantErr:      false,
+		},
+		{
+			name: "1 max retry",
+			config: &RetryConfig{
+				RetryMax: 1,
+				CheckRetry: func(ctx context.Context, resp *nethttp.Response, err error) (bool, error) {
+					return true, nil
+				},
+				Backoff: func(attemptNum int, resp *nethttp.Response) time.Duration {
+					return time.Millisecond
+				},
+			},
+			wantStatus:   nethttp.StatusServiceUnavailable,
+			wantDispatch: 2,
+			wantErr:      false,
+		},
+		{
+			name:         "with no retryConfig",
+			wantStatus:   nethttp.StatusServiceUnavailable,
+			wantDispatch: 1,
+			wantErr:      false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+
+			n := 0
+			var mu sync.Mutex
+			server := httptest.NewServer(nethttp.HandlerFunc(func(writer nethttp.ResponseWriter, request *nethttp.Request) {
+				mu.Lock()
+				n++
+				mu.Unlock()
+
+				writer.WriteHeader(tt.wantStatus)
+			}))
+
+			sender := &HttpMessageSender{
+				Client: nethttp.DefaultClient,
+			}
+
+			request, err := nethttp.NewRequest("POST", server.URL, nil)
+			assert.Nil(t, err)
+			got, err := sender.SendWithRetries(request, tt.config)
+			if (err != nil) != tt.wantErr || got == nil {
+				t.Errorf("SendWithRetries() error = %v, wantErr %v or got nil", err, tt.wantErr)
+				return
+			}
+			if got.StatusCode != nethttp.StatusServiceUnavailable {
+				t.Errorf("SendWithRetries() got = %v, want %v", got.StatusCode, nethttp.StatusServiceUnavailable)
+				return
+			}
+			if n != tt.wantDispatch {
+				t.Errorf("expected %d retries got %d", tt.config.RetryMax, n)
+				return
+			}
+		})
+	}
+}
+
+func TestRetryConfigFromDeliverySpecCheckDelivery(t *testing.T) {
+	linear := eventingduck.BackoffPolicyLinear
+	tests := []struct {
+		name     string
+		spec     eventingduck.DeliverySpec
+		retryMax int
+		wantErr  bool
+	}{
+		{
+			name: "full delivery",
+			spec: eventingduck.DeliverySpec{
+				Retry:         pointer.Int32Ptr(10),
+				BackoffPolicy: &linear,
+				BackoffDelay:  pointer.StringPtr("PT1S"),
+			},
+			retryMax: 10,
+			wantErr:  false,
+		},
+		{
+			name: "only retry",
+			spec: eventingduck.DeliverySpec{
+				Retry:         pointer.Int32Ptr(10),
+				BackoffPolicy: &linear,
+			},
+			retryMax: 10,
+			wantErr:  false,
+		},
+		{
+			name: "not ISO8601",
+			spec: eventingduck.DeliverySpec{
+				Retry:         pointer.Int32Ptr(10),
+				BackoffDelay:  pointer.StringPtr("PP1"),
+				BackoffPolicy: &linear,
+			},
+			retryMax: 10,
+			wantErr:  true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := RetryConfigFromDeliverySpec(tt.spec)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("RetryConfigFromDeliverySpec() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if err != nil {
+				return
+			}
+
+			if got.CheckRetry == nil {
+				t.Errorf("CheckRetry must not be nil")
+				return
+			}
+			if got.Backoff == nil {
+				t.Errorf("Backoff must not be nil")
+			}
+			if got.RetryMax != tt.retryMax {
+				t.Errorf("retryMax want %d got %d", tt.retryMax, got.RetryMax)
+			}
+		})
+	}
+}
diff --git a/test/e2e/helpers/broker_redelivery_helper.go b/test/e2e/helpers/broker_redelivery_helper.go
index 5437a9639c1..d01e7ec0be8 100644
--- a/test/e2e/helpers/broker_redelivery_helper.go
+++ b/test/e2e/helpers/broker_redelivery_helper.go
@@ -40,8 +40,7 @@ func BrokerRedelivery(t *testing.T, creator BrokerCreatorWithRetries) {
 
 	t.Run(dropevents.Fibonacci, func(t *testing.T) {
 		brokerRedelivery(t, creator, numRetries, func(pod *corev1.Pod, client *testlib.Client) error {
-			container := pod.Spec.Containers[0]
-			container.Env = append(container.Env,
+			pod.Spec.Containers[0].Env = append(pod.Spec.Containers[0].Env,
 				corev1.EnvVar{
 					Name:  dropevents.SkipAlgorithmKey,
 					Value: dropevents.Fibonacci,
@@ -53,15 +52,14 @@ func BrokerRedelivery(t *testing.T, creator BrokerCreatorWithRetries) {
 
 	t.Run(dropevents.Sequence, func(t *testing.T) {
 		brokerRedelivery(t, creator, numRetries, func(pod *corev1.Pod, client *testlib.Client) error {
-			container := pod.Spec.Containers[0]
-			container.Env = append(container.Env,
+			pod.Spec.Containers[0].Env = append(pod.Spec.Containers[0].Env,
 				corev1.EnvVar{
 					Name:  dropevents.SkipAlgorithmKey,
 					Value: dropevents.Sequence,
 				},
 				corev1.EnvVar{
 					Name:  dropevents.NumberKey,
-					Value: fmt.Sprintf("%d", numRetries-1),
+					Value: fmt.Sprintf("%d", numRetries),
 				},
 			)
 			return nil