diff --git a/.tool-versions b/.tool-versions
new file mode 100644
index 0000000..1c44dd0
--- /dev/null
+++ b/.tool-versions
@@ -0,0 +1 @@
+ruby 2.6.6
diff --git a/app/mailers/rails_jwt_auth/mailer.rb b/app/mailers/rails_jwt_auth/mailer.rb
index 6969e1b..014d3b3 100644
--- a/app/mailers/rails_jwt_auth/mailer.rb
+++ b/app/mailers/rails_jwt_auth/mailer.rb
@@ -2,9 +2,13 @@
   class RailsJwtAuth::Mailer < ApplicationMailer
     default from: RailsJwtAuth.mailer_sender
 
-    def confirmation_instructions(user)
+    before_action do
+      @user = RailsJwtAuth.model.find(params[:user_id])
+      @subject = I18n.t("rails_jwt_auth.mailer.#{action_name}.subject")
+    end
+
+    def confirmation_instructions
       raise RailsJwtAuth::NotConfirmationsUrl unless RailsJwtAuth.confirmations_url.present?
-      @user = user
 
       @confirmations_url = add_param_to_url(
         RailsJwtAuth.confirmations_url,
@@ -12,19 +16,15 @@ def confirmation_instructions(user)
         @user.confirmation_token
       )
 
-      subject = I18n.t('rails_jwt_auth.mailer.confirmation_instructions.subject')
-      mail(to: @user.unconfirmed_email || @user[RailsJwtAuth.email_field_name], subject: subject)
+      mail(to: @user.unconfirmed_email || @user[RailsJwtAuth.email_field_name], subject: @subject)
     end
 
-    def email_changed(user)
-      @user = user
-      subject = I18n.t('rails_jwt_auth.mailer.email_changed.subject')
-      mail(to: @user[RailsJwtAuth.email_field_name!], subject: subject)
+    def email_changed
+      mail(to: @user[RailsJwtAuth.email_field_name!], subject: @subject)
     end
 
-    def reset_password_instructions(user)
+    def reset_password_instructions
       raise RailsJwtAuth::NotResetPasswordsUrl unless RailsJwtAuth.reset_passwords_url.present?
-      @user = user
 
       @reset_passwords_url = add_param_to_url(
         RailsJwtAuth.reset_passwords_url,
@@ -32,13 +32,11 @@ def reset_password_instructions(user)
         @user.reset_password_token
       )
 
-      subject = I18n.t('rails_jwt_auth.mailer.reset_password_instructions.subject')
-      mail(to: @user[RailsJwtAuth.email_field_name], subject: subject)
+      mail(to: @user[RailsJwtAuth.email_field_name], subject: @subject)
     end
 
-    def set_password_instructions(user)
+    def set_password_instructions
       raise RailsJwtAuth::NotSetPasswordsUrl unless RailsJwtAuth.set_passwords_url.present?
-      @user = user
 
       @reset_passwords_url = add_param_to_url(
         RailsJwtAuth.set_passwords_url,
@@ -46,13 +44,11 @@ def set_password_instructions(user)
         @user.reset_password_token
       )
 
-      subject = I18n.t('rails_jwt_auth.mailer.set_password_instructions.subject')
-      mail(to: @user[RailsJwtAuth.email_field_name], subject: subject)
+      mail(to: @user[RailsJwtAuth.email_field_name], subject: @subject)
     end
 
-    def send_invitation(user)
+    def send_invitation
       raise RailsJwtAuth::NotInvitationsUrl unless RailsJwtAuth.invitations_url.present?
-      @user = user
 
       @invitations_url = add_param_to_url(
         RailsJwtAuth.invitations_url,
@@ -60,17 +56,13 @@ def send_invitation(user)
         @user.invitation_token
       )
 
-      subject = I18n.t('rails_jwt_auth.mailer.send_invitation.subject')
-      mail(to: @user[RailsJwtAuth.email_field_name], subject: subject)
+      mail(to: @user[RailsJwtAuth.email_field_name], subject: @subject)
     end
 
-    def send_unlock_instructions(user)
-      @user = user
-      subject = I18n.t('rails_jwt_auth.mailer.send_unlock_instructions.subject')
-
+    def send_unlock_instructions
       @unlock_url = add_param_to_url(RailsJwtAuth.unlock_url, 'unlock_token', @user.unlock_token)
 
-      mail(to: @user[RailsJwtAuth.email_field_name], subject: subject)
+      mail(to: @user[RailsJwtAuth.email_field_name], subject: @subject)
     end
 
     protected
diff --git a/app/models/concerns/rails_jwt_auth/confirmable.rb b/app/models/concerns/rails_jwt_auth/confirmable.rb
index 0cefba1..765f059 100644
--- a/app/models/concerns/rails_jwt_auth/confirmable.rb
+++ b/app/models/concerns/rails_jwt_auth/confirmable.rb
@@ -34,12 +34,10 @@ def self.included(base)
             self.confirmation_token = SecureRandom.base58(24)
             self.confirmation_sent_at = Time.current
 
-            mailer = Mailer.confirmation_instructions(self)
-            RailsJwtAuth.deliver_later ? mailer.deliver_later : mailer.deliver
+            RailsJwtAuth.send_email(:confirmation_instructions, self)
 
             if RailsJwtAuth.send_email_changed_notification
-              mailer = Mailer.email_changed(self)
-              RailsJwtAuth.deliver_later ? mailer.deliver_later : mailer.deliver
+              RailsJwtAuth.send_email(:email_changed, self)
             end
           end
         end
@@ -58,8 +56,7 @@ def send_confirmation_instructions
       self.confirmation_sent_at = Time.current
       return false unless save
 
-      mailer = Mailer.confirmation_instructions(self)
-      RailsJwtAuth.deliver_later ? mailer.deliver_later : mailer.deliver
+      RailsJwtAuth.send_email(:confirmation_instructions, self)
       true
     end
 
diff --git a/app/models/concerns/rails_jwt_auth/invitable.rb b/app/models/concerns/rails_jwt_auth/invitable.rb
index 4faf9c1..4abc451 100644
--- a/app/models/concerns/rails_jwt_auth/invitable.rb
+++ b/app/models/concerns/rails_jwt_auth/invitable.rb
@@ -112,9 +112,8 @@ def generate_invitation_token
     end
 
     def send_invitation_mail
-      RailsJwtAuth.email_field_name! # ensure email field es valid
-      mailer = Mailer.send_invitation(self)
-      RailsJwtAuth.deliver_later ? mailer.deliver_later : mailer.deliver
+      RailsJwtAuth.email_field_name! # ensure email field is valid
+      RailsJwtAuth.send_email(:send_invitation, self)
     end
 
     def invitation_period_valid?
diff --git a/app/models/concerns/rails_jwt_auth/lockable.rb b/app/models/concerns/rails_jwt_auth/lockable.rb
index 43162aa..a0c0cb6 100644
--- a/app/models/concerns/rails_jwt_auth/lockable.rb
+++ b/app/models/concerns/rails_jwt_auth/lockable.rb
@@ -68,8 +68,7 @@ def send_unlock_instructions
       self.unlock_token = SecureRandom.base58(24)
       save(validate: false)
 
-      mailer = Mailer.send_unlock_instructions(self)
-      RailsJwtAuth.deliver_later ? mailer.deliver_later : mailer.deliver
+      RailsJwtAuth.send_email(:send_unlock_instructions, self)
     end
 
     def access_locked?
diff --git a/app/models/concerns/rails_jwt_auth/recoverable.rb b/app/models/concerns/rails_jwt_auth/recoverable.rb
index 903c38d..319fdcc 100644
--- a/app/models/concerns/rails_jwt_auth/recoverable.rb
+++ b/app/models/concerns/rails_jwt_auth/recoverable.rb
@@ -40,8 +40,7 @@ def send_reset_password_instructions
       self.reset_password_sent_at = Time.current
       return false unless save
 
-      mailer = Mailer.reset_password_instructions(self)
-      RailsJwtAuth.deliver_later ? mailer.deliver_later : mailer.deliver
+      RailsJwtAuth.send_email(:reset_password_instructions, self)
     end
 
     def set_and_send_password_instructions
@@ -56,8 +55,7 @@ def set_and_send_password_instructions
       self.reset_password_sent_at = Time.current
       return false unless save
 
-      mailer = Mailer.set_password_instructions(self)
-      RailsJwtAuth.deliver_later ? mailer.deliver_later : mailer.deliver
+      RailsJwtAuth.send_email(:set_password_instructions, self)
       true
     end
 
diff --git a/lib/rails_jwt_auth.rb b/lib/rails_jwt_auth.rb
index 177c825..f1aa433 100644
--- a/lib/rails_jwt_auth.rb
+++ b/lib/rails_jwt_auth.rb
@@ -114,4 +114,9 @@ def self.email_field_name!
 
     field_name
   end
+
+  def self.send_email(method, user)
+    mailer = RailsJwtAuth::Mailer.with(user_id: user.id.to_s).public_send(method)
+    RailsJwtAuth.deliver_later ? mailer.deliver_later : mailer.deliver
+  end
 end
diff --git a/spec/controllers/confirmations_controller_spec.rb b/spec/controllers/confirmations_controller_spec.rb
index bf0104e..f51ae1b 100644
--- a/spec/controllers/confirmations_controller_spec.rb
+++ b/spec/controllers/confirmations_controller_spec.rb
@@ -18,15 +18,9 @@
           end
 
           it 'sends new confirmation email with new token' do
-            class Mock
-              def deliver
-              end
-            end
-
-            expect(RailsJwtAuth::Mailer).to receive(:confirmation_instructions)
-              .with(user).and_return(Mock.new)
-
             old_token = user.confirmation_token
+            expect(RailsJwtAuth).to receive(:send_email).with(:confirmation_instructions, anything)
+
             post :create, params: {confirmation: {email: user.email}}
             expect(user.reload.confirmation_token).not_to eq(old_token)
           end
diff --git a/spec/controllers/passwords_controller_spec.rb b/spec/controllers/passwords_controller_spec.rb
index 96795a6..408bfec 100644
--- a/spec/controllers/passwords_controller_spec.rb
+++ b/spec/controllers/passwords_controller_spec.rb
@@ -29,13 +29,8 @@
           end
 
           it 'sends new reset_password email with new token' do
-            class Mock
-              def deliver
-              end
-            end
-
-            expect(RailsJwtAuth::Mailer).to receive(:reset_password_instructions)
-              .with(user).and_return(Mock.new)
+            expect(RailsJwtAuth).to receive(:send_email)
+              .with(:reset_password_instructions, anything)
 
             old_token = user.reset_password_token
             post :create, params: {password: {email: user.email}}
diff --git a/spec/lib/rails_jwt_auth_spec.rb b/spec/lib/rails_jwt_auth_spec.rb
new file mode 100644
index 0000000..cea6c55
--- /dev/null
+++ b/spec/lib/rails_jwt_auth_spec.rb
@@ -0,0 +1,41 @@
+require 'rails_helper'
+
+describe RailsJwtAuth do
+  before(:all) { RailsJwtAuth.model_name = "ActiveRecordUser" }
+
+  describe '#send_email' do
+    let(:unconfirmed_user) { FactoryBot.create(:active_record_unconfirmed_user) }
+
+    after { RailsJwtAuth.deliver_later = false }
+
+    context 'when deliver_later options is false' do
+      before { RailsJwtAuth.deliver_later = false }
+
+      it 'uses deliver method' do
+        mock2 = OpenStruct.new(deliver: true)
+        mock = OpenStruct.new(confirmation_instructions: mock2)
+
+        expect(RailsJwtAuth::Mailer).to receive(:with).with(user_id: unconfirmed_user.id.to_s)
+                                                     .and_return(mock)
+        expect(mock2).to receive(:deliver)
+
+        RailsJwtAuth.send_email(:confirmation_instructions, unconfirmed_user)
+      end
+    end
+
+    context 'when deliver_later options is false' do
+      before { RailsJwtAuth.deliver_later = true }
+
+      it 'uses deliver method' do
+        mock2 = OpenStruct.new(deliver_later: true)
+        mock = OpenStruct.new(confirmation_instructions: mock2)
+
+        expect(RailsJwtAuth::Mailer).to receive(:with).with(user_id: unconfirmed_user.id.to_s)
+                                                     .and_return(mock)
+        expect(mock2).to receive(:deliver_later)
+
+        RailsJwtAuth.send_email(:confirmation_instructions, unconfirmed_user)
+      end
+    end
+  end
+end
diff --git a/spec/mailers/mailer_spec.rb b/spec/mailers/mailer_spec.rb
index 066abca..8d97393 100644
--- a/spec/mailers/mailer_spec.rb
+++ b/spec/mailers/mailer_spec.rb
@@ -1,13 +1,17 @@
 require 'rails_helper'
 
 RSpec.describe RailsJwtAuth::Mailer, type: :mailer do
+  before(:all) { RailsJwtAuth.model_name = 'ActiveRecordUser' }
+
+  let(:mail_params) { {user_id: user.id.to_s } }
+
   describe 'confirmation_instructions' do
     let(:user) do
       FactoryBot.create(:active_record_unconfirmed_user,
                          confirmation_token: 'abcd', confirmation_sent_at: Time.current)
     end
 
-    let(:mail) { described_class.confirmation_instructions(user).deliver_now }
+    let(:mail) { described_class.with(mail_params).confirmation_instructions.deliver_now }
     let(:url) { "#{RailsJwtAuth.confirmations_url}?confirmation_token=#{user.confirmation_token}" }
 
     it 'sends email with correct info' do
@@ -46,7 +50,7 @@
                                              reset_password_sent_at: Time.current)
     end
 
-    let(:mail) { described_class.reset_password_instructions(user).deliver_now }
+    let(:mail) { described_class.with(mail_params).reset_password_instructions.deliver_now }
     let(:url) { "#{RailsJwtAuth.reset_passwords_url}?reset_password_token=#{user.reset_password_token}" }
 
     it 'sends email with correct info' do
@@ -75,7 +79,7 @@
                                              reset_password_sent_at: Time.current)
     end
 
-    let(:mail) { described_class.set_password_instructions(user).deliver_now }
+    let(:mail) { described_class.with(mail_params).set_password_instructions.deliver_now }
     let(:url) { "#{RailsJwtAuth.set_passwords_url}?reset_password_token=#{user.reset_password_token}" }
 
     it 'sends email with correct info' do
@@ -104,7 +108,7 @@
                                              invitation_created_at: Time.current)
     end
 
-    let(:mail) { described_class.send_invitation(user).deliver_now }
+    let(:mail) { described_class.with(mail_params).send_invitation.deliver_now }
     let(:url) { "#{RailsJwtAuth.invitations_url}?invitation_token=#{user.invitation_token}" }
 
     it 'sends email with correct info' do
@@ -136,7 +140,7 @@
       )
     end
 
-    let(:mail) { described_class.send_unlock_instructions(user).deliver_now }
+    let(:mail) { described_class.with(mail_params).send_unlock_instructions.deliver_now }
     let(:url) { "#{RailsJwtAuth.unlock_url}?unlock_token=#{user.unlock_token}" }
 
     it 'sends email with correct info' do
diff --git a/spec/models/concerns/confirmable_spec.rb b/spec/models/concerns/confirmable_spec.rb
index 3cf3299..219b1bb 100644
--- a/spec/models/concerns/confirmable_spec.rb
+++ b/spec/models/concerns/confirmable_spec.rb
@@ -71,45 +71,18 @@
       end
 
       describe '#send_confirmation_instructions' do
-        before :all do
-          class Mock
-            def deliver
-            end
-
-            def deliver_later
-            end
-          end
-        end
-
         it 'fills confirmation fields' do
-          mock = Mock.new
-          allow(RailsJwtAuth::Mailer).to receive(:confirmation_instructions).and_return(mock)
           unconfirmed_user.send_confirmation_instructions
           expect(unconfirmed_user.confirmation_token).not_to be_nil
           expect(unconfirmed_user.confirmation_sent_at).not_to be_nil
         end
 
         it 'sends confirmation email' do
-          mock = Mock.new
           new_user = FactoryBot.build("#{orm.underscore}_unconfirmed_user")
-          allow(RailsJwtAuth::Mailer).to receive(:confirmation_instructions).and_return(mock)
-          expect(mock).to receive(:deliver)
+          expect(RailsJwtAuth).to receive(:send_email).with(:confirmation_instructions, anything)
           new_user.send_confirmation_instructions
         end
 
-        context 'when use deliver_later option' do
-          before { RailsJwtAuth.deliver_later = true }
-          after  { RailsJwtAuth.deliver_later = false }
-
-          it 'uses deliver_later method to send email' do
-            mock = Mock.new
-            new_user = FactoryBot.build("#{orm.underscore}_unconfirmed_user")
-            allow(RailsJwtAuth::Mailer).to receive(:confirmation_instructions).and_return(mock)
-            expect(mock).to receive(:deliver_later)
-            new_user.send_confirmation_instructions
-          end
-        end
-
         context 'when user is confirmed' do
           it 'returns false' do
             expect(user.send_confirmation_instructions).to eq(false)
@@ -121,9 +94,9 @@ def deliver_later
           end
 
           it 'does not send confirmation email' do
-            mock = Mock.new
-            allow(RailsJwtAuth::Mailer).to receive(:confirmation_instructions).and_return(mock)
-            expect(mock).not_to receive(:deliver)
+            expect(RailsJwtAuth).not_to receive(:send_email)
+              .with(:confirmation_instructions, anything)
+
             user.send_confirmation_instructions
           end
 
@@ -174,22 +147,19 @@ def deliver_later
           context 'when send_email_changed_notification option is false' do
             it 'sends only confirmation email' do
               allow(RailsJwtAuth).to receive(:send_email_changed_notification).and_return(false)
+              expect(RailsJwtAuth).to receive(:send_email).with(:confirmation_instructions, user)
+              expect(RailsJwtAuth).not_to receive(:send_email).with(:email_changed, user)
               user.update(email: 'new@email.com')
-              expect(ActionMailer::Base.deliveries.count).to eq(1)
-              expect(ActionMailer::Base.deliveries.first.subject).to eq('Confirmation instructions')
-              expect(ActionMailer::Base.deliveries.first.to).to eq(['new@email.com'])
             end
           end
 
           context 'when send_email_changed_notification option is true' do
             it 'sends confirmation and nofication email' do
               allow(RailsJwtAuth).to receive(:send_email_changed_notification).and_return(true)
+              expect(RailsJwtAuth).to receive(:send_email).with(:email_changed, user)
+              expect(RailsJwtAuth).to receive(:send_email).with(:confirmation_instructions, user)
               old_email = user.email
               user.update(email: 'new@email.com')
-              expect(ActionMailer::Base.deliveries.first.subject).to eq('Confirmation instructions')
-              expect(ActionMailer::Base.deliveries.first.to).to eq(['new@email.com'])
-              expect(ActionMailer::Base.deliveries.last.subject).to eq('Email changed')
-              expect(ActionMailer::Base.deliveries.last.to).to eq([old_email])
             end
           end
         end
diff --git a/spec/models/concerns/recoverable_spec.rb b/spec/models/concerns/recoverable_spec.rb
index 62c5c2e..f0e0d0a 100644
--- a/spec/models/concerns/recoverable_spec.rb
+++ b/spec/models/concerns/recoverable_spec.rb
@@ -1,16 +1,6 @@
 require 'rails_helper'
 
 describe RailsJwtAuth::Recoverable do
-  before :all do
-    class Mock
-      def deliver
-      end
-
-      def deliver_later
-      end
-    end
-  end
-
   %w(ActiveRecord Mongoid).each do |orm|
     context "when use #{orm}" do
       before(:all) { RailsJwtAuth.model_name = "#{orm}User" }
@@ -24,8 +14,6 @@ def deliver_later
 
       describe '#send_reset_password_instructions' do
         it 'fills reset password fields' do
-          mock = Mock.new
-          allow(RailsJwtAuth::Mailer).to receive(:reset_password_instructions).and_return(mock)
           user.send_reset_password_instructions
           user.reload
           expect(user.reset_password_token).not_to be_nil
@@ -33,24 +21,10 @@ def deliver_later
         end
 
         it 'sends reset password email' do
-          mock = Mock.new
-          allow(RailsJwtAuth::Mailer).to receive(:reset_password_instructions).and_return(mock)
-          expect(mock).to receive(:deliver)
+          expect(RailsJwtAuth).to receive(:send_email).with(:reset_password_instructions, user)
           user.send_reset_password_instructions
         end
 
-        context 'when use deliver_later option' do
-          before { RailsJwtAuth.deliver_later = true }
-          after  { RailsJwtAuth.deliver_later = false }
-
-          it 'uses deliver_later method to send email' do
-            mock = Mock.new
-            allow(RailsJwtAuth::Mailer).to receive(:reset_password_instructions).and_return(mock)
-            expect(mock).to receive(:deliver_later)
-            user.send_reset_password_instructions
-          end
-        end
-
         context 'when user is unconfirmed' do
           let(:user) { FactoryBot.create("#{orm.underscore}_unconfirmed_user") }
 
@@ -66,7 +40,9 @@ def deliver_later
           end
 
           it 'doe not send reset password email' do
-            expect(RailsJwtAuth::Mailer).not_to receive(:reset_password_instructions)
+            expect(RailsJwtAuth).not_to receive(:send_email)
+              .with(:reset_password_instructions, user)
+
             user.send_reset_password_instructions
           end
         end
@@ -106,8 +82,6 @@ def deliver_later
         let(:user) { FactoryBot.build("#{orm.underscore}_user", password: nil) }
 
         it 'set password and confirm' do
-          mock = Mock.new
-          allow(RailsJwtAuth::Mailer).to receive(:reset_password_instructions).and_return(mock)
           user.set_and_send_password_instructions
           user.reload
           expect(user.password).not_to be_nil
@@ -115,8 +89,6 @@ def deliver_later
         end
 
         it 'fills set password fields' do
-          mock = Mock.new
-          allow(RailsJwtAuth::Mailer).to receive(:reset_password_instructions).and_return(mock)
           user.set_and_send_password_instructions
           user.reload
           expect(user.reset_password_token).not_to be_nil
@@ -124,23 +96,9 @@ def deliver_later
         end
 
         it 'sends set password email' do
-          mock = Mock.new
-          allow(RailsJwtAuth::Mailer).to receive(:set_password_instructions).and_return(mock)
-          expect(mock).to receive(:deliver)
+          expect(RailsJwtAuth).to receive(:send_email).with(:set_password_instructions, user)
           user.set_and_send_password_instructions
         end
-
-        context 'when use deliver_later option' do
-          before { RailsJwtAuth.deliver_later = true }
-          after  { RailsJwtAuth.deliver_later = false }
-
-          it 'uses deliver_later method to send email' do
-            mock = Mock.new
-            allow(RailsJwtAuth::Mailer).to receive(:set_password_instructions).and_return(mock)
-            expect(mock).to receive(:deliver_later)
-            user.set_and_send_password_instructions
-          end
-        end
       end
 
       describe '#before_save' do