Bamboo SentEmailViewerPlug undefined

I do have an issue with mentioned function. This is the error from browser:

function Bamboo.SentEmailViewerPlug.init/1 is undefined (module Bamboo.SentEmailViewerPlug is not available)

And this is from console :

[error] #PID<0.868.0> running RewardappWeb.Endpoint (connection #PID<0.829.0>, stream id 4) terminated
Server: localhost:4000 (http)
Request: GET /mailbox
** (exit) an exception was raised:
    ** (UndefinedFunctionError) function Bamboo.SentEmailViewerPlug.init/1 is undefined (module Bamboo.SentEmailViewerPlug is not available)
        (phoenix 1.6.6) lib/phoenix/router/route.ex:41:
        (phoenix 1.6.6) lib/phoenix/router.ex:355: Phoenix.Router.__call__/2
        (rewardapp 0.1.0) lib/rewardapp_web/endpoint.ex:1: RewardappWeb.Endpoint.plug_builder_call/2
        (rewardapp 0.1.0) lib/plug/debugger.ex:136: RewardappWeb.Endpoint."call (overridable 3)"/2
        (rewardapp 0.1.0) lib/rewardapp_web/endpoint.ex:1:
        (phoenix 1.6.6) lib/phoenix/endpoint/cowboy2_handler.ex:54: Phoenix.Endpoint.Cowboy2Handler.init/4
        (cowboy 2.9.0) /Users/mateuszosinski/Desktop/elixir/rewardapp/deps/cowboy/src/cowboy_handler.erl:37: :cowboy_handler.execute/2
        (cowboy 2.9.0) /Users/mateuszosinski/Desktop/elixir/rewardapp/deps/cowboy/src/cowboy_stream_h.erl:306: :cowboy_stream_h.execute/3
        (cowboy 2.9.0) /Users/mateuszosinski/Desktop/elixir/rewardapp/deps/cowboy/src/cowboy_stream_h.erl:295: :cowboy_stream_h.request_process/3
        (stdlib 3.17.1) proc_lib.erl:226: :proc_lib.init_p_do_apply/3

Here is my router.ex file :

defmodule RewardappWeb.Router do
  use RewardappWeb, :router
  use Phoenix.Router

  pipeline :browser do
    plug :accepts, ["html"]
    plug :fetch_session
    plug :fetch_live_flash
    plug :put_root_layout, {RewardappWeb.LayoutView, :root}
    plug :protect_from_forgery
    plug :put_secure_browser_headers

  pipeline :api do
    plug :accepts, ["json"]

  scope "/", RewardappWeb do
    pipe_through :browser

    #get "/", PageController, :index
    #get "/users", GrantController, :login
    get "/admin", GrantController, :admin
    get "/main", GrantController, :main
    get "/", GrantController, :index
    post "/", GrantController, :login
    get "/add", GrantController, :add
    post "/add/:id", GrantController, :update
    get "/admin/delete/:id", GrantController, :delete


  if Mix.env == :dev do
    forward "/mailbox", Bamboo.SentEmailViewerPlug

  # Other scopes may use custom stacks.
  # scope "/api", RewardappWeb do
  #   pipe_through :api
  # end

  # Enables LiveDashboard only for development
  # If you want to use the LiveDashboard in production, you should put
  # it behind authentication and allow only admins to access it.
  # If your application does not have an admins-only section yet,
  # you can use Plug.BasicAuth to set up some basic authentication
  # as long as you are also using SSL (which you should anyway).
  if Mix.env() in [:dev, :test] do
    import Phoenix.LiveDashboard.Router

    scope "/" do
      pipe_through :browser

      live_dashboard "/dashboard", metrics: RewardappWeb.Telemetry

  # Enables the Swoosh mailbox preview in development.
  # Note that preview only shows emails that were sent by the same
  # node running the Phoenix server.
  if Mix.env() == :dev do
    scope "/dev" do
      pipe_through :browser

      #forward "/mailbox", Plug.Swoosh.MailboxPreview

Mails are being sent totally fine - I have inspected that with IO.inspect, and right now, they are sent fine. However, I can not attempt to see localhost:4000/mailbox. Where is my mistake? Thank you in advance!!

The solution is Bamboo.EmailPreviewPlug instead of Bamboo.SentEmailViewerPlug.

What Bamboo version are you using? The plug has been called Bamboo.SentEmailViewerPlug for years.

However, on higher versions (such as 1.5) it did not work either, unfortunately :frowning:

Bamboo 0.8 was released 5 years ago. It is amazing that it still works with the very recent v1.6.6 Phoenix. What a testament of the API stability in Elixir/Phoenix.