diff --git a/app/channel.go b/app/channel.go
index 66c9cd3047..3eaf2f5ef6 100644
--- a/app/channel.go
+++ b/app/channel.go
@@ -2503,7 +2503,7 @@ func (a *App) MarkChannelAsUnreadFromPost(postID string, userID string, collapse
 		if threadMembership == nil {
 			opts := store.ThreadMembershipOpts{
 				Following:             followThread,
-				IncrementMentions:     true,
+				IncrementMentions:     false,
 				UpdateFollowing:       true,
 				UpdateViewedTimestamp: true,
 				UpdateParticipants:    false,
diff --git a/app/channel_test.go b/app/channel_test.go
index 5aacfba1db..69796ec606 100644
--- a/app/channel_test.go
+++ b/app/channel_test.go
@@ -2212,37 +2212,136 @@ func TestMarkUnreadWithThreads(t *testing.T) {
 		*cfg.ServiceSettings.CollapsedThreads = model.COLLAPSED_THREADS_DEFAULT_ON
 	})
 
-	rootPost, appErr := th.App.CreatePost(th.Context, &model.Post{UserId: th.BasicUser2.Id, CreateAt: model.GetMillis(), ChannelId: th.BasicChannel.Id, Message: "hi"}, th.BasicChannel, false, false)
-	require.Nil(t, appErr)
-	replyPost, appErr := th.App.CreatePost(th.Context, &model.Post{RootId: rootPost.Id, UserId: th.BasicUser2.Id, CreateAt: model.GetMillis(), ChannelId: th.BasicChannel.Id, Message: "hi"}, th.BasicChannel, false, false)
-	require.Nil(t, appErr)
-	threads, appErr := th.App.GetThreadsForUser(th.BasicUser.Id, th.BasicTeam.Id, model.GetUserThreadsOpts{})
-	require.Nil(t, appErr)
-	require.Zero(t, threads.Total)
+	t.Run("Follow threads only if specified", func(t *testing.T) {
+		rootPost, appErr := th.App.CreatePost(th.Context, &model.Post{UserId: th.BasicUser2.Id, CreateAt: model.GetMillis(), ChannelId: th.BasicChannel.Id, Message: "hi"}, th.BasicChannel, false, false)
+		require.Nil(t, appErr)
+		replyPost, appErr := th.App.CreatePost(th.Context, &model.Post{RootId: rootPost.Id, UserId: th.BasicUser2.Id, CreateAt: model.GetMillis(), ChannelId: th.BasicChannel.Id, Message: "hi"}, th.BasicChannel, false, false)
+		require.Nil(t, appErr)
+		threads, appErr := th.App.GetThreadsForUser(th.BasicUser.Id, th.BasicTeam.Id, model.GetUserThreadsOpts{})
+		require.Nil(t, appErr)
+		require.Zero(t, threads.Total)
 
-	_, appErr = th.App.MarkChannelAsUnreadFromPost(replyPost.Id, th.BasicUser.Id, true, true)
-	require.Nil(t, appErr)
+		_, appErr = th.App.MarkChannelAsUnreadFromPost(replyPost.Id, th.BasicUser.Id, true, true)
+		require.Nil(t, appErr)
 
-	threads, appErr = th.App.GetThreadsForUser(th.BasicUser.Id, th.BasicTeam.Id, model.GetUserThreadsOpts{})
-	require.Nil(t, appErr)
-	require.NotZero(t, threads.Total)
+		threads, appErr = th.App.GetThreadsForUser(th.BasicUser.Id, th.BasicTeam.Id, model.GetUserThreadsOpts{})
+		require.Nil(t, appErr)
+		require.NotZero(t, threads.Total)
 
-	threadMembership, appErr := th.App.GetThreadMembershipForUser(th.BasicUser.Id, replyPost.RootId)
-	require.Nil(t, appErr)
-	require.NotNil(t, threadMembership)
-	assert.True(t, threadMembership.Following)
+		threadMembership, appErr := th.App.GetThreadMembershipForUser(th.BasicUser.Id, replyPost.RootId)
+		require.Nil(t, appErr)
+		require.NotNil(t, threadMembership)
+		assert.True(t, threadMembership.Following)
 
-	// Create a new thread
-	rootPost, appErr = th.App.CreatePost(th.Context, &model.Post{UserId: th.BasicUser2.Id, CreateAt: model.GetMillis(), ChannelId: th.BasicChannel.Id, Message: "hi2"}, th.BasicChannel, false, false)
-	require.Nil(t, appErr)
-	replyPost, appErr = th.App.CreatePost(th.Context, &model.Post{RootId: rootPost.Id, UserId: th.BasicUser2.Id, CreateAt: model.GetMillis(), ChannelId: th.BasicChannel.Id, Message: "hi2"}, th.BasicChannel, false, false)
-	require.Nil(t, appErr)
+		// Create a new thread
+		rootPost, appErr = th.App.CreatePost(th.Context, &model.Post{UserId: th.BasicUser2.Id, CreateAt: model.GetMillis(), ChannelId: th.BasicChannel.Id, Message: "hi2"}, th.BasicChannel, false, false)
+		require.Nil(t, appErr)
+		replyPost, appErr = th.App.CreatePost(th.Context, &model.Post{RootId: rootPost.Id, UserId: th.BasicUser2.Id, CreateAt: model.GetMillis(), ChannelId: th.BasicChannel.Id, Message: "hi2"}, th.BasicChannel, false, false)
+		require.Nil(t, appErr)
 
-	_, appErr = th.App.MarkChannelAsUnreadFromPost(replyPost.Id, th.BasicUser.Id, true, false)
-	require.Nil(t, appErr)
+		_, appErr = th.App.MarkChannelAsUnreadFromPost(replyPost.Id, th.BasicUser.Id, true, false)
+		require.Nil(t, appErr)
 
-	threadMembership, appErr = th.App.GetThreadMembershipForUser(th.BasicUser.Id, replyPost.RootId)
-	require.Nil(t, appErr)
-	require.NotNil(t, threadMembership)
-	assert.False(t, threadMembership.Following)
+		threadMembership, appErr = th.App.GetThreadMembershipForUser(th.BasicUser.Id, replyPost.RootId)
+		require.Nil(t, appErr)
+		require.NotNil(t, threadMembership)
+		assert.False(t, threadMembership.Following)
+	})
+
+	t.Run("Set unread mentions correctly", func(t *testing.T) {
+		t.Run("Never followed root post with no replies or mentions", func(t *testing.T) {
+			rootPost, appErr := th.App.CreatePost(th.Context, &model.Post{UserId: th.BasicUser2.Id, CreateAt: model.GetMillis(), ChannelId: th.BasicChannel.Id, Message: "hi"}, th.BasicChannel, false, false)
+			require.Nil(t, appErr)
+			_, appErr = th.App.MarkChannelAsUnreadFromPost(rootPost.Id, th.BasicUser.Id, true, true)
+			require.Nil(t, appErr)
+
+			threadMembership, appErr := th.App.GetThreadMembershipForUser(th.BasicUser.Id, rootPost.Id)
+			require.Nil(t, appErr)
+			require.NotNil(t, threadMembership)
+			assert.Zero(t, threadMembership.UnreadMentions)
+		})
+
+		t.Run("Never followed root post with replies and no mentions", func(t *testing.T) {
+			rootPost, appErr := th.App.CreatePost(th.Context, &model.Post{UserId: th.BasicUser2.Id, CreateAt: model.GetMillis(), ChannelId: th.BasicChannel.Id, Message: "hi"}, th.BasicChannel, false, false)
+			require.Nil(t, appErr)
+			_, appErr = th.App.CreatePost(th.Context, &model.Post{RootId: rootPost.Id, UserId: th.BasicUser2.Id, CreateAt: model.GetMillis(), ChannelId: th.BasicChannel.Id, Message: "hi"}, th.BasicChannel, false, false)
+			require.Nil(t, appErr)
+			_, appErr = th.App.MarkChannelAsUnreadFromPost(rootPost.Id, th.BasicUser.Id, true, true)
+			require.Nil(t, appErr)
+
+			threadMembership, appErr := th.App.GetThreadMembershipForUser(th.BasicUser.Id, rootPost.Id)
+			require.Nil(t, appErr)
+			require.NotNil(t, threadMembership)
+			assert.Zero(t, threadMembership.UnreadMentions)
+		})
+
+		t.Run("Never followed root post with replies and mentions", func(t *testing.T) {
+			rootPost, appErr := th.App.CreatePost(th.Context, &model.Post{UserId: th.BasicUser2.Id, CreateAt: model.GetMillis(), ChannelId: th.BasicChannel.Id, Message: "hi"}, th.BasicChannel, false, false)
+			require.Nil(t, appErr)
+			_, appErr = th.App.CreatePost(th.Context, &model.Post{RootId: rootPost.Id, UserId: th.BasicUser2.Id, CreateAt: model.GetMillis(), ChannelId: th.BasicChannel.Id, Message: "hi @" + th.BasicUser.Username}, th.BasicChannel, false, false)
+			require.Nil(t, appErr)
+			_, appErr = th.App.MarkChannelAsUnreadFromPost(rootPost.Id, th.BasicUser.Id, true, true)
+			require.Nil(t, appErr)
+
+			threadMembership, appErr := th.App.GetThreadMembershipForUser(th.BasicUser.Id, rootPost.Id)
+			require.Nil(t, appErr)
+			require.NotNil(t, threadMembership)
+			assert.Equal(t, int64(1), threadMembership.UnreadMentions)
+		})
+
+		t.Run("Previously followed root post with no replies or mentions", func(t *testing.T) {
+			rootPost, appErr := th.App.CreatePost(th.Context, &model.Post{UserId: th.BasicUser2.Id, CreateAt: model.GetMillis(), ChannelId: th.BasicChannel.Id, Message: "hi"}, th.BasicChannel, false, false)
+			require.Nil(t, appErr)
+			appErr = th.App.UpdateThreadFollowForUser(th.BasicUser.Id, th.BasicTeam.Id, rootPost.Id, true)
+			require.Nil(t, appErr)
+			appErr = th.App.UpdateThreadFollowForUser(th.BasicUser.Id, th.BasicTeam.Id, rootPost.Id, false)
+			require.Nil(t, appErr)
+
+			_, appErr = th.App.MarkChannelAsUnreadFromPost(rootPost.Id, th.BasicUser.Id, true, true)
+			require.Nil(t, appErr)
+
+			threadMembership, appErr := th.App.GetThreadMembershipForUser(th.BasicUser.Id, rootPost.Id)
+			require.Nil(t, appErr)
+			require.NotNil(t, threadMembership)
+			assert.Zero(t, threadMembership.UnreadMentions)
+		})
+
+		t.Run("Previously followed root post with replies and no mentions", func(t *testing.T) {
+			rootPost, appErr := th.App.CreatePost(th.Context, &model.Post{UserId: th.BasicUser2.Id, CreateAt: model.GetMillis(), ChannelId: th.BasicChannel.Id, Message: "hi"}, th.BasicChannel, false, false)
+			require.Nil(t, appErr)
+			_, appErr = th.App.CreatePost(th.Context, &model.Post{RootId: rootPost.Id, UserId: th.BasicUser2.Id, CreateAt: model.GetMillis(), ChannelId: th.BasicChannel.Id, Message: "hi"}, th.BasicChannel, false, false)
+			require.Nil(t, appErr)
+			appErr = th.App.UpdateThreadFollowForUser(th.BasicUser.Id, th.BasicTeam.Id, rootPost.Id, true)
+			require.Nil(t, appErr)
+			appErr = th.App.UpdateThreadFollowForUser(th.BasicUser.Id, th.BasicTeam.Id, rootPost.Id, false)
+			require.Nil(t, appErr)
+
+			_, appErr = th.App.MarkChannelAsUnreadFromPost(rootPost.Id, th.BasicUser.Id, true, true)
+			require.Nil(t, appErr)
+
+			threadMembership, appErr := th.App.GetThreadMembershipForUser(th.BasicUser.Id, rootPost.Id)
+			require.Nil(t, appErr)
+			require.NotNil(t, threadMembership)
+			assert.Zero(t, threadMembership.UnreadMentions)
+		})
+
+		t.Run("Previously followed root post with replies and mentions", func(t *testing.T) {
+			rootPost, appErr := th.App.CreatePost(th.Context, &model.Post{UserId: th.BasicUser2.Id, CreateAt: model.GetMillis(), ChannelId: th.BasicChannel.Id, Message: "hi"}, th.BasicChannel, false, false)
+			require.Nil(t, appErr)
+			_, appErr = th.App.CreatePost(th.Context, &model.Post{RootId: rootPost.Id, UserId: th.BasicUser2.Id, CreateAt: model.GetMillis(), ChannelId: th.BasicChannel.Id, Message: "hi @" + th.BasicUser.Username}, th.BasicChannel, false, false)
+			require.Nil(t, appErr)
+			appErr = th.App.UpdateThreadFollowForUser(th.BasicUser.Id, th.BasicTeam.Id, rootPost.Id, true)
+			require.Nil(t, appErr)
+			appErr = th.App.UpdateThreadFollowForUser(th.BasicUser.Id, th.BasicTeam.Id, rootPost.Id, false)
+			require.Nil(t, appErr)
+
+			_, appErr = th.App.MarkChannelAsUnreadFromPost(rootPost.Id, th.BasicUser.Id, true, true)
+			require.Nil(t, appErr)
+
+			threadMembership, appErr := th.App.GetThreadMembershipForUser(th.BasicUser.Id, rootPost.Id)
+			require.Nil(t, appErr)
+			require.NotNil(t, threadMembership)
+			assert.Equal(t, int64(1), threadMembership.UnreadMentions)
+		})
+	})
 }
diff --git a/app/user.go b/app/user.go
index 4eb072e583..a733f65cb6 100644
--- a/app/user.go
+++ b/app/user.go
@@ -2228,14 +2228,17 @@ func (a *App) UpdateThreadFollowForUser(userID, teamID, threadID string, state b
 		return model.NewAppError("UpdateThreadFollowForUser", "app.user.update_thread_follow_for_user.app_error", nil, err.Error(), http.StatusInternalServerError)
 	}
 	thread, err := a.Srv().Store.Thread().Get(threadID)
-
 	if err != nil {
 		return model.NewAppError("UpdateThreadFollowForUser", "app.user.update_thread_follow_for_user.app_error", nil, err.Error(), http.StatusInternalServerError)
 	}
+	replyCount := int64(0)
+	if thread != nil {
+		replyCount = thread.ReplyCount
+	}
 	message := model.NewWebSocketEvent(model.WEBSOCKET_EVENT_THREAD_FOLLOW_CHANGED, teamID, "", userID, nil)
 	message.Add("thread_id", threadID)
 	message.Add("state", state)
-	message.Add("reply_count", thread.ReplyCount)
+	message.Add("reply_count", replyCount)
 	a.Publish(message)
 	return nil
 }
diff --git a/store/sqlstore/thread_store.go b/store/sqlstore/thread_store.go
index 5fb43b41d6..5eae3c8564 100644
--- a/store/sqlstore/thread_store.go
+++ b/store/sqlstore/thread_store.go
@@ -110,7 +110,7 @@ func (s *SqlThreadStore) get(ex gorp.SqlExecutor, id string) (*model.Thread, err
 	err := ex.SelectOne(&thread, query, args...)
 	if err != nil {
 		if err == sql.ErrNoRows {
-			return nil, store.NewErrNotFound("Thread", id)
+			return nil, nil
 		}
 
 		return nil, errors.Wrapf(err, "failed to get thread with id=%s", id)
@@ -626,7 +626,7 @@ func (s *SqlThreadStore) MaintainMembership(userId, postId string, opts store.Th
 		if getErr != nil {
 			return nil, getErr
 		}
-		if !thread.Participants.Contains(userId) {
+		if thread != nil && !thread.Participants.Contains(userId) {
 			thread.Participants = append(thread.Participants, userId)
 			if _, err = s.update(trx, thread); err != nil {
 				return nil, err
diff --git a/store/storetest/thread_store.go b/store/storetest/thread_store.go
index 46e380f282..1eaba518b5 100644
--- a/store/storetest/thread_store.go
+++ b/store/storetest/thread_store.go
@@ -469,8 +469,9 @@ func testThreadStorePermanentDeleteBatchForRetentionPolicies(t *testing.T, ss st
 	nowMillis := thread.LastReplyAt + *channelPolicy.PostDuration*24*60*60*1000 + 1
 	_, _, err = ss.Thread().PermanentDeleteBatchForRetentionPolicies(nowMillis, 0, limit, model.RetentionPolicyCursor{})
 	require.NoError(t, err)
-	_, err = ss.Thread().Get(post.Id)
-	require.Error(t, err, "thread should have been deleted by channel policy")
+	thread, err = ss.Thread().Get(post.Id)
+	assert.NoError(t, err)
+	assert.Nil(t, thread, "thread should have been deleted by channel policy")
 
 	// create a new thread
 	threadStoreCreateReply(t, ss, channel.Id, post.Id, 2000)
@@ -498,8 +499,9 @@ func testThreadStorePermanentDeleteBatchForRetentionPolicies(t *testing.T, ss st
 	require.NoError(t, err)
 	_, _, err = ss.Thread().PermanentDeleteBatchForRetentionPolicies(nowMillis, 0, limit, model.RetentionPolicyCursor{})
 	require.NoError(t, err)
-	_, err = ss.Thread().Get(post.Id)
-	require.Error(t, err, "thread should have been deleted by team policy")
+	thread, err = ss.Thread().Get(post.Id)
+	assert.NoError(t, err)
+	assert.Nil(t, thread, "thread should have been deleted by team policy")
 }
 
 func testThreadStorePermanentDeleteBatchThreadMembershipsForRetentionPolicies(t *testing.T, ss store.Store) {