Rails Tutorial 「11.4 本番環境でのメール送信」で送信できない

前提・実現したいこと

Rails Tutorial 「11.4 本番環境でのメール送信」でアカウント有効化メールを送信したいです

発生している問題・エラーメッセージ

We're sorry, but something went wrong.
If you are the application owner check the logs for more information.

$ heroku addons:create sendgrid:starter
を実行し表示されたリンクからSendGridを設定しました。
自分のメールアドレスでユーザー新規登録をしましたがメールが届かず上記のエラーが表示されました。

その際のログは以下の通りです。
$ heroku logs -t

2020-05-04T03:22:36.282345+00:00 app[web.1]: D, [2020-05-04T03:22:36.282215 #4] DEBUG -- : [6dc709b8-942d-4be6-81d8-a38ce83c367c] UserMailer#account_activation: processed outbound mail in 274.2ms
2020-05-04T03:22:36.318882+00:00 app[web.1]: I, [2020-05-04T03:22:36.318752 #4]  INFO -- : [6dc709b8-942d-4be6-81d8-a38ce83c367c] Sent mail to ******@gmail.com (36.3ms)
2020-05-04T03:22:36.318925+00:00 app[web.1]: D, [2020-05-04T03:22:36.318864 #4] DEBUG -- : [6dc709b8-942d-4be6-81d8-a38ce83c367c] Date: Mon, 04 May 2020 03:22:36 +0000
2020-05-04T03:22:36.318927+00:00 app[web.1]: From: noreply@example.com
2020-05-04T03:22:36.318927+00:00 app[web.1]: To: ******@gmail.com
2020-05-04T03:22:36.318928+00:00 app[web.1]: Message-ID: <5eaf8a7c46137_42abee1dc3c58923b9@ea10cc4f-d1f2-4ad8-9de2-617dbd66d6d2.mail>
2020-05-04T03:22:36.318928+00:00 app[web.1]: Subject: Account activation
2020-05-04T03:22:36.318928+00:00 app[web.1]: Mime-Version: 1.0
2020-05-04T03:22:36.318929+00:00 app[web.1]: Content-Type: multipart/alternative;
2020-05-04T03:22:36.318930+00:00 app[web.1]: boundary="--==_mimepart_5eaf8a7c44945_42abee1dc3c58922bf";
2020-05-04T03:22:36.318930+00:00 app[web.1]: charset=UTF-8
2020-05-04T03:22:36.318931+00:00 app[web.1]: Content-Transfer-Encoding: 7bit
2020-05-04T03:22:36.318931+00:00 app[web.1]: 
2020-05-04T03:22:36.318931+00:00 app[web.1]: 
2020-05-04T03:22:36.318933+00:00 app[web.1]: ----==_mimepart_5eaf8a7c44945_42abee1dc3c58922bf
2020-05-04T03:22:36.318933+00:00 app[web.1]: Content-Type: text/plain;
2020-05-04T03:22:36.318934+00:00 app[web.1]: charset=UTF-8
2020-05-04T03:22:36.318934+00:00 app[web.1]: Content-Transfer-Encoding: 7bit
2020-05-04T03:22:36.318934+00:00 app[web.1]: 
2020-05-04T03:22:36.318935+00:00 app[web.1]: Hi AAAAA
2020-05-04T03:22:36.318935+00:00 app[web.1]: 
2020-05-04T03:22:36.318936+00:00 app[web.1]: Welcome to the Sample App! Click on the link below to activate your account:
2020-05-04T03:22:36.318936+00:00 app[web.1]: 
2020-05-04T03:22:36.318936+00:00 app[web.1]: https://mysterious-harbor-17577.herokuapp.com/account_activations/N5Xk4VMMvEdu-Oe5pz-D7w/edit?email=******%40gmail.com
2020-05-04T03:22:36.318937+00:00 app[web.1]: 
2020-05-04T03:22:36.318937+00:00 app[web.1]: 
2020-05-04T03:22:36.318937+00:00 app[web.1]: ----==_mimepart_5eaf8a7c44945_42abee1dc3c58922bf
2020-05-04T03:22:36.318938+00:00 app[web.1]: Content-Type: text/html;
2020-05-04T03:22:36.318938+00:00 app[web.1]: charset=UTF-8
2020-05-04T03:22:36.318938+00:00 app[web.1]: Content-Transfer-Encoding: 7bit
2020-05-04T03:22:36.318939+00:00 app[web.1]: 
2020-05-04T03:22:36.318939+00:00 app[web.1]: <!DOCTYPE html>
2020-05-04T03:22:36.318940+00:00 app[web.1]: <html>
2020-05-04T03:22:36.318940+00:00 app[web.1]: <head>
2020-05-04T03:22:36.318941+00:00 app[web.1]: <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
2020-05-04T03:22:36.318941+00:00 app[web.1]: <style>
2020-05-04T03:22:36.318941+00:00 app[web.1]: /* Email styles need to be inline */
2020-05-04T03:22:36.318942+00:00 app[web.1]: </style>
2020-05-04T03:22:36.318942+00:00 app[web.1]: </head>
2020-05-04T03:22:36.318942+00:00 app[web.1]: 
2020-05-04T03:22:36.318943+00:00 app[web.1]: <body>
2020-05-04T03:22:36.318943+00:00 app[web.1]: <h1>Sample App</h1>
2020-05-04T03:22:36.318943+00:00 app[web.1]: 
2020-05-04T03:22:36.318944+00:00 app[web.1]: <p>Hi AAAAA,</p>
2020-05-04T03:22:36.318944+00:00 app[web.1]: 
2020-05-04T03:22:36.318944+00:00 app[web.1]: <p>
2020-05-04T03:22:36.318945+00:00 app[web.1]: Welcome to the Sample App! Click on the link below to activate your account:
2020-05-04T03:22:36.318945+00:00 app[web.1]: </p>
2020-05-04T03:22:36.318945+00:00 app[web.1]: 
2020-05-04T03:22:36.318946+00:00 app[web.1]: <a href="https://mysterious-harbor-17577.herokuapp.com/account_activations/N5Xk4VMMvEdu-Oe5pz-D7w/edit?email=******%40gmail.com">Activate</a>
2020-05-04T03:22:36.318946+00:00 app[web.1]: 
2020-05-04T03:22:36.318946+00:00 app[web.1]: </body>
2020-05-04T03:22:36.318947+00:00 app[web.1]: </html>
2020-05-04T03:22:36.318947+00:00 app[web.1]: 
2020-05-04T03:22:36.318947+00:00 app[web.1]: ----==_mimepart_5eaf8a7c44945_42abee1dc3c58922bf--
2020-05-04T03:22:36.318947+00:00 app[web.1]: 
2020-05-04T03:22:36.319162+00:00 app[web.1]: I, [2020-05-04T03:22:36.319096 #4]  INFO -- : [6dc709b8-942d-4be6-81d8-a38ce83c367c] Completed 500 Internal Server Error in 476ms (ActiveRecord: 6.5ms)
2020-05-04T03:22:36.319625+00:00 app[web.1]: F, [2020-05-04T03:22:36.319548 #4] FATAL -- : [6dc709b8-942d-4be6-81d8-a38ce83c367c]
2020-05-04T03:22:36.319660+00:00 app[web.1]: F, [2020-05-04T03:22:36.319605 #4] FATAL -- : [6dc709b8-942d-4be6-81d8-a38ce83c367c] Net::SMTPFatalError (550 Unauthenticated senders not allowed
2020-05-04T03:22:36.319661+00:00 app[web.1]: ):
2020-05-04T03:22:36.319705+00:00 app[web.1]: F, [2020-05-04T03:22:36.319658 #4] FATAL -- : [6dc709b8-942d-4be6-81d8-a38ce83c367c]
2020-05-04T03:22:36.319784+00:00 app[web.1]: F, [2020-05-04T03:22:36.319708 #4] FATAL -- : [6dc709b8-942d-4be6-81d8-a38ce83c367c] app/models/user.rb:42:in `send_activation_email'
2020-05-04T03:22:36.319785+00:00 app[web.1]: [6dc709b8-942d-4be6-81d8-a38ce83c367c] app/controllers/users_controller.rb:23:in `create'
2020-05-04T03:22:36.813152+00:00 heroku[router]: at=info method=GET path="/favicon.ico" host=mysterious-harbor-17577.herokuapp.com request_id=6a459610-4ec1-4e3a-b8cd-9706ef732891 fwd="162.230.251.4" dyno=web.1 connect=0ms service=2ms status=304 bytes=112 protocol=https

文面は作成されているようですがメールは届いていません。
以下のメッセージがあるのでuser.rbとusers_controller.rbに原因があるのかもしれませんが、見つけられません。
Completed 500 Internal Server Error in 301ms (ActiveRecord: 16.4ms)
Net::SMTPFatalError (550 Unauthenticated senders not allowed
app/models/user.rb:42:in send_activation_email' app/controllers/users_controller.rb:23:in create'

rails
1(user.rb)
2class User < ApplicationRecord
3  attr_accessor :remember_token, :activation_token
4  before_save :downcase_email
5  before_create :create_activation_digest
6  validates :name, presence: true, length: { maximum: 50 } 
7  VALID_EMAIL_REGEX = /\A[\w+\-.]+@[a-z\d\-]+(.[a-z\d\-]+)*.[a-z]+\z/i
8  validates :email, presence: true, length: { maximum: 255 }, format: { with: VALID_EMAIL_REGEX }, uniqueness: {case_sensitive: false}
9  has_secure_password
10  validates :password, presence: true, length: { minimum: 6 }, allow_nil: true
11  
12  def User.digest(string) # 渡された文字列のハッシュ値を返す.
13    cost = ActiveModel::SecurePassword.min_cost ? BCrypt::Engine::MIN_COST :
14                                                  BCrypt::Engine.cost
15    BCrypt::Password.create(string, cost: cost)
16  end
17  
18  def User.new_token # ランダムなトークンを返す
19    SecureRandom.urlsafe_base64
20  end
21  
22  def remember
23    self.remember_token = User.new_token
24    update_attribute(:remember_digest, User.digest(remember_token))
25  end
26  
27  def authenticated?(attribute, token)
28    digest = send("#{attribute}_digest")
29    return false if digest.nil?
30    BCrypt::Password.new(digest).is_password?(token)
31  end
32  
33  def forget
34    update_attribute(:remember_digest, nil)
35  end
36
37  def activate
38    update_attribute(:activated,    true)
39    update_attribute(:activated_at, Time.zone.now)
40  end
41
42  def send_activation_email
43    UserMailer.account_activation(self).deliver_now
44  end
45    
46  private
47  
48  def downcase_email
49    self.email = email.downcase
50  end
51  
52  def create_activation_digest
53    self.activation_token = User.new_token
54    self.activation_digest = User.digest(activation_token)
55  end
56  
57end

rails
1(users_controller.rb)
2class UsersController < ApplicationController
3  before_action :logged_in_user,only:[:index,:edit,:update,:destroy]
4  before_action :correct_user, only:[:edit,:update]
5  before_action :admin_user,     only: :destroy
6
7  def index
8    @users = User.paginate(page: params[:page])
9  end
10
11
12  def new
13    @user = User.new
14  end
15
16
17  def show
18    @user = User.find(params[:id])
19  end
20
21  def create
22    @user = User.new(user_params)
23    if @user.save
24      @user.send_activation_email
25      flash[:info] = "Please check your email to activate your account."
26      redirect_to root_url
27    else
28      render 'new'
29    end
30  end
31
32
33  def edit
34    @user = User.find(params[:id]) 
35  end
36
37  def update
38    @user = User.find(params[:id])
39    if @user.update_attributes(user_params)
40      #更新に成功した場合扱う
41      flash[:success] = "Profile updated"
42      redirect_to @user
43    else
44      render 'edit'
45    end
46  end
47
48  def destroy
49    User.find(params[:id]).destroy
50    flash[:success] = "User deleted"
51    redirect_to users_url
52  end
53
54  private
55
56    def user_params
57      params.require(:user).permit(:name, :email, :password,
58                                   :password_confirmation)
59    end
60
61     #ログイン済みユーザーかどうか確認
62    def logged_in_user
63      unless logged_in?
64        store_location
65        flash[:danger] = "Please log in"
66        redirect_to login_url
67      end
68    end
69
70    #正しいユーザーかどうか確認
71    def correct_user
72      @user = User.find(params[:id])
73      redirect_to(root_url) unless current_user?(@user)
74    end
75
76    #管理者かどうか確認
77    def admin_user
78      redirect_to(root_url) unless current_user.admin?
79    end
80
81
82end