diff --git a/app/app_iface.go b/app/app_iface.go
index 7302cc69a8..3eb8ac9ed9 100644
--- a/app/app_iface.go
+++ b/app/app_iface.go
@@ -884,8 +884,8 @@ type AppIface interface {
 	SearchUsersNotInTeam(notInTeamId string, term string, options *model.UserSearchOptions) ([]*model.User, *model.AppError)
 	SearchUsersWithoutTeam(term string, options *model.UserSearchOptions) ([]*model.User, *model.AppError)
 	SendAckToPushProxy(ack *model.PushNotificationAck) error
-	SendAutoResponse(channel *model.Channel, receiver *model.User) (bool, *model.AppError)
-	SendAutoResponseIfNecessary(channel *model.Channel, sender *model.User) (bool, *model.AppError)
+	SendAutoResponse(channel *model.Channel, receiver *model.User, post *model.Post) (bool, *model.AppError)
+	SendAutoResponseIfNecessary(channel *model.Channel, sender *model.User, post *model.Post) (bool, *model.AppError)
 	SendEmailVerification(user *model.User, newEmail, redirect string) *model.AppError
 	SendEphemeralPost(userId string, post *model.Post) *model.Post
 	SendNotifications(post *model.Post, team *model.Team, channel *model.Channel, sender *model.User, parentPostList *model.PostList, setOnline bool) ([]string, error)
diff --git a/app/auto_responder.go b/app/auto_responder.go
index 56d2d195d5..fd92aa5031 100644
--- a/app/auto_responder.go
+++ b/app/auto_responder.go
@@ -8,7 +8,7 @@ import (
 	"github.com/mattermost/mattermost-server/v5/model"
 )
 
-func (a *App) SendAutoResponseIfNecessary(channel *model.Channel, sender *model.User) (bool, *model.AppError) {
+func (a *App) SendAutoResponseIfNecessary(channel *model.Channel, sender *model.User, post *model.Post) (bool, *model.AppError) {
 	if channel.Type != model.CHANNEL_DIRECT {
 		return false, nil
 	}
@@ -28,10 +28,10 @@ func (a *App) SendAutoResponseIfNecessary(channel *model.Channel, sender *model.
 		return false, err
 	}
 
-	return a.SendAutoResponse(channel, receiver)
+	return a.SendAutoResponse(channel, receiver, post)
 }
 
-func (a *App) SendAutoResponse(channel *model.Channel, receiver *model.User) (bool, *model.AppError) {
+func (a *App) SendAutoResponse(channel *model.Channel, receiver *model.User, post *model.Post) (bool, *model.AppError) {
 	if receiver == nil || receiver.NotifyProps == nil {
 		return false, nil
 	}
@@ -43,11 +43,15 @@ func (a *App) SendAutoResponse(channel *model.Channel, receiver *model.User) (bo
 		return false, nil
 	}
 
+	rootID := post.Id
+	if post.RootId != "" {
+		rootID = post.RootId
+	}
+
 	autoResponderPost := &model.Post{
 		ChannelId: channel.Id,
 		Message:   message,
-		RootId:    "",
-		ParentId:  "",
+		RootId:    rootID,
 		Type:      model.POST_AUTO_RESPONDER,
 		UserId:    receiver.Id,
 	}
diff --git a/app/auto_responder_test.go b/app/auto_responder_test.go
index 6ed9d674b9..7b61103b25 100644
--- a/app/auto_responder_test.go
+++ b/app/auto_responder_test.go
@@ -97,7 +97,14 @@ func TestSendAutoResponseIfNecessary(t *testing.T) {
 
 		channel := th.CreateDmChannel(receiver)
 
-		sent, err := th.App.SendAutoResponseIfNecessary(channel, th.BasicUser)
+		savedPost, _ := th.App.CreatePost(&model.Post{
+			ChannelId: channel.Id,
+			Message:   "zz" + model.NewId() + "a",
+			UserId:    th.BasicUser.Id},
+			th.BasicChannel,
+			false, true)
+
+		sent, err := th.App.SendAutoResponseIfNecessary(channel, th.BasicUser, savedPost)
 
 		assert.Nil(t, err)
 		assert.True(t, sent)
@@ -120,7 +127,14 @@ func TestSendAutoResponseIfNecessary(t *testing.T) {
 
 		channel := th.CreateDmChannel(receiver)
 
-		sent, err := th.App.SendAutoResponseIfNecessary(channel, th.BasicUser)
+		savedPost, _ := th.App.CreatePost(&model.Post{
+			ChannelId: channel.Id,
+			Message:   "zz" + model.NewId() + "a",
+			UserId:    th.BasicUser.Id},
+			th.BasicChannel,
+			false, true)
+
+		sent, err := th.App.SendAutoResponseIfNecessary(channel, th.BasicUser, savedPost)
 
 		assert.Nil(t, err)
 		assert.False(t, sent)
@@ -130,7 +144,14 @@ func TestSendAutoResponseIfNecessary(t *testing.T) {
 		th := Setup(t).InitBasic()
 		defer th.TearDown()
 
-		sent, err := th.App.SendAutoResponseIfNecessary(th.BasicChannel, th.BasicUser)
+		savedPost, _ := th.App.CreatePost(&model.Post{
+			ChannelId: th.BasicChannel.Id,
+			Message:   "zz" + model.NewId() + "a",
+			UserId:    th.BasicUser.Id},
+			th.BasicChannel,
+			false, true)
+
+		sent, err := th.App.SendAutoResponseIfNecessary(th.BasicChannel, th.BasicUser, savedPost)
 
 		assert.Nil(t, err)
 		assert.False(t, sent)
@@ -163,7 +184,14 @@ func TestSendAutoResponseIfNecessary(t *testing.T) {
 		botUser, err := th.App.GetUser(bot.UserId)
 		assert.Nil(t, err)
 
-		sent, err := th.App.SendAutoResponseIfNecessary(channel, botUser)
+		savedPost, _ := th.App.CreatePost(&model.Post{
+			ChannelId: channel.Id,
+			Message:   "zz" + model.NewId() + "a",
+			UserId:    botUser.Id},
+			th.BasicChannel,
+			false, true)
+
+		sent, err := th.App.SendAutoResponseIfNecessary(channel, botUser, savedPost)
 
 		assert.Nil(t, err)
 		assert.False(t, sent)
@@ -185,29 +213,80 @@ func TestSendAutoResponseSuccess(t *testing.T) {
 	userUpdated1, err := th.App.PatchUser(user.Id, patch, true)
 	require.Nil(t, err)
 
-	th.App.CreatePost(&model.Post{
+	savedPost, _ := th.App.CreatePost(&model.Post{
 		ChannelId: th.BasicChannel.Id,
 		Message:   "zz" + model.NewId() + "a",
 		UserId:    th.BasicUser.Id},
 		th.BasicChannel,
 		false, true)
 
-	sent, err := th.App.SendAutoResponse(th.BasicChannel, userUpdated1)
+	sent, err := th.App.SendAutoResponse(th.BasicChannel, userUpdated1, savedPost)
 
 	assert.Nil(t, err)
 	assert.True(t, sent)
 
-	if list, err := th.App.GetPosts(th.BasicChannel.Id, 0, 1); err != nil {
-		require.Nil(t, err)
-	} else {
-		autoResponderPostFound := false
-		for _, post := range list.Posts {
-			if post.Type == model.POST_AUTO_RESPONDER {
-				autoResponderPostFound = true
-			}
+	list, err := th.App.GetPosts(th.BasicChannel.Id, 0, 1)
+	require.Nil(t, err)
+
+	autoResponderPostFound := false
+	for _, post := range list.Posts {
+		if post.Type == model.POST_AUTO_RESPONDER {
+			autoResponderPostFound = true
+			assert.Equal(t, savedPost.Id, post.RootId)
+			assert.Equal(t, savedPost.Id, post.ParentId)
 		}
-		assert.True(t, autoResponderPostFound)
 	}
+	assert.True(t, autoResponderPostFound)
+}
+
+func TestSendAutoResponseSuccessOnThread(t *testing.T) {
+	th := Setup(t).InitBasic()
+	defer th.TearDown()
+
+	user := th.CreateUser()
+	defer th.App.PermanentDeleteUser(user)
+
+	patch := &model.UserPatch{}
+	patch.NotifyProps = make(map[string]string)
+	patch.NotifyProps["auto_responder_active"] = "true"
+	patch.NotifyProps["auto_responder_message"] = "Hello, I'm unavailable today."
+
+	userUpdated1, err := th.App.PatchUser(user.Id, patch, true)
+	require.Nil(t, err)
+
+	parentPost, _ := th.App.CreatePost(&model.Post{
+		ChannelId: th.BasicChannel.Id,
+		Message:   "zz" + model.NewId() + "a",
+		UserId:    th.BasicUser.Id},
+		th.BasicChannel,
+		false, true)
+
+	savedPost, _ := th.App.CreatePost(&model.Post{
+		ChannelId: th.BasicChannel.Id,
+		Message:   "zz" + model.NewId() + "a",
+		UserId:    th.BasicUser.Id,
+		RootId:    parentPost.Id,
+		ParentId:  parentPost.Id},
+		th.BasicChannel,
+		false, true)
+
+	sent, err := th.App.SendAutoResponse(th.BasicChannel, userUpdated1, savedPost)
+
+	assert.Nil(t, err)
+	assert.True(t, sent)
+
+	list, err := th.App.GetPosts(th.BasicChannel.Id, 0, 1)
+	require.Nil(t, err)
+
+	autoResponderPostFound := false
+	for _, post := range list.Posts {
+		if post.Type == model.POST_AUTO_RESPONDER {
+			autoResponderPostFound = true
+			assert.Equal(t, savedPost.RootId, post.RootId)
+			assert.Equal(t, savedPost.ParentId, post.ParentId)
+		}
+	}
+	assert.True(t, autoResponderPostFound)
 }
 
 func TestSendAutoResponseFailure(t *testing.T) {
@@ -225,14 +304,14 @@ func TestSendAutoResponseFailure(t *testing.T) {
 	userUpdated1, err := th.App.PatchUser(user.Id, patch, true)
 	require.Nil(t, err)
 
-	th.App.CreatePost(&model.Post{
+	savedPost, _ := th.App.CreatePost(&model.Post{
 		ChannelId: th.BasicChannel.Id,
 		Message:   "zz" + model.NewId() + "a",
 		UserId:    th.BasicUser.Id},
 		th.BasicChannel,
 		false, true)
 
-	sent, err := th.App.SendAutoResponse(th.BasicChannel, userUpdated1)
+	sent, err := th.App.SendAutoResponse(th.BasicChannel, userUpdated1, savedPost)
 
 	assert.Nil(t, err)
 	assert.False(t, sent)
diff --git a/app/opentracing/opentracing_layer.go b/app/opentracing/opentracing_layer.go
index 23b18d10b2..8e2f1109b4 100644
--- a/app/opentracing/opentracing_layer.go
+++ b/app/opentracing/opentracing_layer.go
@@ -12895,7 +12895,7 @@ func (a *OpenTracingAppLayer) SendAckToPushProxy(ack *model.PushNotificationAck)
 	return resultVar0
 }
 
-func (a *OpenTracingAppLayer) SendAutoResponse(channel *model.Channel, receiver *model.User) (bool, *model.AppError) {
+func (a *OpenTracingAppLayer) SendAutoResponse(channel *model.Channel, receiver *model.User, post *model.Post) (bool, *model.AppError) {
 	origCtx := a.ctx
 	span, newCtx := tracing.StartSpanWithParentByContext(a.ctx, "app.SendAutoResponse")
 
@@ -12907,7 +12907,7 @@ func (a *OpenTracingAppLayer) SendAutoResponse(channel *model.Channel, receiver
 	}()
 
 	defer span.Finish()
-	resultVar0, resultVar1 := a.app.SendAutoResponse(channel, receiver)
+	resultVar0, resultVar1 := a.app.SendAutoResponse(channel, receiver, post)
 
 	if resultVar1 != nil {
 		span.LogFields(spanlog.Error(resultVar1))
@@ -12917,7 +12917,7 @@ func (a *OpenTracingAppLayer) SendAutoResponse(channel *model.Channel, receiver
 	return resultVar0, resultVar1
 }
 
-func (a *OpenTracingAppLayer) SendAutoResponseIfNecessary(channel *model.Channel, sender *model.User) (bool, *model.AppError) {
+func (a *OpenTracingAppLayer) SendAutoResponseIfNecessary(channel *model.Channel, sender *model.User, post *model.Post) (bool, *model.AppError) {
 	origCtx := a.ctx
 	span, newCtx := tracing.StartSpanWithParentByContext(a.ctx, "app.SendAutoResponseIfNecessary")
 
@@ -12929,7 +12929,7 @@ func (a *OpenTracingAppLayer) SendAutoResponseIfNecessary(channel *model.Channel
 	}()
 
 	defer span.Finish()
-	resultVar0, resultVar1 := a.app.SendAutoResponseIfNecessary(channel, sender)
+	resultVar0, resultVar1 := a.app.SendAutoResponseIfNecessary(channel, sender, post)
 
 	if resultVar1 != nil {
 		span.LogFields(spanlog.Error(resultVar1))
diff --git a/app/post.go b/app/post.go
index da731f8f2a..c24b2857f6 100644
--- a/app/post.go
+++ b/app/post.go
@@ -451,7 +451,7 @@ func (a *App) handlePostEvents(post *model.Post, user *model.User, channel *mode
 
 	if post.Type != model.POST_AUTO_RESPONDER { // don't respond to an auto-responder
 		a.Srv().Go(func() {
-			_, err := a.SendAutoResponseIfNecessary(channel, user)
+			_, err := a.SendAutoResponseIfNecessary(channel, user, post)
 			if err != nil {
 				mlog.Error("Failed to send auto response", mlog.String("user_id", user.Id), mlog.String("post_id", post.Id), mlog.Err(err))
 			}