diff --git a/app/controllers/admin/email_controller.rb b/app/controllers/admin/email_controller.rb
index 779bd875829..ce97d029d79 100644
--- a/app/controllers/admin/email_controller.rb
+++ b/app/controllers/admin/email_controller.rb
@@ -167,11 +167,13 @@ class Admin::EmailController < Admin::AdminController
       end
     end
 
-    # TODO: 2022-05-01 Remove this route once all sites have migrated over
-    # to using the new email_encoded param.
     if deprecated_email_param_used
-      render plain:
-               "warning: the email parameter is deprecated. all POST requests to this route should be sent with a base64 strict encoded email_encoded parameter instead. email has been received and is queued for processing"
+      warning =
+        "warning: the email parameter is deprecated. all POST requests to this route should be sent with a base64 strict encoded email_encoded parameter instead. email has been received and is queued for processing"
+
+      Discourse.deprecate(warning, drop_from: "3.3.0")
+
+      render plain: warning
     else
       render plain: "email has been received and is queued for processing"
     end
diff --git a/app/jobs/regular/toggle_topic_closed.rb b/app/jobs/regular/toggle_topic_closed.rb
index a02831ca61c..6a1c811eead 100644
--- a/app/jobs/regular/toggle_topic_closed.rb
+++ b/app/jobs/regular/toggle_topic_closed.rb
@@ -1,10 +1,13 @@
 # frozen_string_literal: true
 
 module Jobs
-  # TODO: DEPRECATED - Use OpenTopic and CloseTopic instead.
-  # (martin - 2021-05-01) - Delete once topic timer revamp is completed.
   class ToggleTopicClosed < ::Jobs::Base
     def execute(args)
+      Discourse.deprecate(
+        "ToggleTopicClosed is deprecated. Use OpenTopic and CloseTopic instead.",
+        drop_from: "3.3.0",
+      )
+
       topic_timer = TopicTimer.find_by(id: args[:topic_timer_id] || args[:topic_status_update_id])
 
       # state false is Open Topic
diff --git a/app/models/user.rb b/app/models/user.rb
index bb93fbd5ec9..e46f31349ef 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -659,11 +659,11 @@ class User < ActiveRecord::Base
     results.to_h
   end
 
-  ###
-  # DEPRECATED: This is only maintained for backwards compat until v2.5. There
-  # may be inconsistencies with counts in the UI because of this, because unread
-  # high priority includes PMs AND bookmark reminders.
   def unread_private_messages
+    Discourse.deprecate(
+      "#unread_private_messages is deprecated, use #unread_high_priority_notifications instead.",
+      drop_from: "2.5.0",
+    )
     @unread_pms ||= unread_high_priority_notifications
   end
 
diff --git a/app/serializers/queued_post_serializer.rb b/app/serializers/queued_post_serializer.rb
index 91d64f26bfb..b8f59be95b7 100644
--- a/app/serializers/queued_post_serializer.rb
+++ b/app/serializers/queued_post_serializer.rb
@@ -1,6 +1,5 @@
 # frozen_string_literal: true
 
-# Deprecated, should be removed once users have sufficient opportunity to do so
 class QueuedPostSerializer < ApplicationSerializer
   attributes(
     :id,
@@ -19,6 +18,11 @@ class QueuedPostSerializer < ApplicationSerializer
   has_one :created_by, serializer: AdminUserListSerializer, root: :users
   has_one :topic, serializer: BasicTopicSerializer
 
+  def initialize(object, options = {})
+    Discourse.deprecate("QueuedPostSerializer is deprecated.", drop_from: "3.3.0")
+    super
+  end
+
   def queue
     "default"
   end