diff --git a/app/mailers/notification_mailer.rb b/app/mailers/notification_mailer.rb
index 6ebe4cec262..61be19fe366 100644
--- a/app/mailers/notification_mailer.rb
+++ b/app/mailers/notification_mailer.rb
@@ -6,7 +6,7 @@
 # The subject and body of a Notification can be customized by each demarche.
 #
 class NotificationMailer < ApplicationMailer
-  before_action :set_dossier
+  before_action :set_dossier, except: [:send_notification_for_tiers]
   before_action :set_services_publics_plus, only: :send_notification
 
   helper ServiceHelper
@@ -24,6 +24,21 @@ def send_notification
     end
   end
 
+  def send_notification_for_tiers(dossier)
+    @dossier = dossier
+
+    if @dossier.individual.no_notification?
+      mail.perform_deliveries = false
+      return
+    end
+
+    @subject = "Votre dossier rempli par le mandataire #{@dossier.mandataire_first_name} #{@dossier.mandataire_last_name} a été mis à jour"
+    @email = @dossier.individual.email
+    @logo_url = procedure_logo_url(@dossier.procedure)
+
+    mail(subject: @subject, to: @email, template_name: 'send_notification_for_tiers')
+  end
+
   def self.send_en_construction_notification(dossier)
     with(dossier: dossier, state: Dossier.states.fetch(:en_construction)).send_notification
   end
diff --git a/app/models/dossier.rb b/app/models/dossier.rb
index 8e062a62a5c..66158267992 100644
--- a/app/models/dossier.rb
+++ b/app/models/dossier.rb
@@ -884,6 +884,7 @@ def after_passer_en_construction
     save!
     MailTemplatePresenterService.create_commentaire_for_state(self)
     NotificationMailer.send_en_construction_notification(self).deliver_later
+    NotificationMailer.send_notification_for_tiers(self).deliver_later if self.for_tiers?
     procedure.compute_dossiers_count
     RoutingEngine.compute(self)
   end
@@ -918,6 +919,7 @@ def after_passer_en_instruction(h)
     MailTemplatePresenterService.create_commentaire_for_state(self)
     if !disable_notification
       NotificationMailer.send_en_instruction_notification(self).deliver_later
+      NotificationMailer.send_notification_for_tiers(self).deliver_later if self.for_tiers?
     end
     log_dossier_operation(instructeur, :passer_en_instruction)
   end
@@ -934,6 +936,7 @@ def after_passer_automatiquement_en_instruction
     save!
     MailTemplatePresenterService.create_commentaire_for_state(self)
     NotificationMailer.send_en_instruction_notification(self).deliver_later
+    NotificationMailer.send_notification_for_tiers(self).deliver_later if self.for_tiers?
 
     if procedure.sva_svr_enabled?
       # TODO: handle serialization errors when SIRET demandeur was not completed
@@ -1011,6 +1014,7 @@ def after_accepter(h)
     MailTemplatePresenterService.create_commentaire_for_state(self)
     if !disable_notification
       NotificationMailer.send_accepte_notification(self).deliver_later
+      NotificationMailer.send_notification_for_tiers(self).deliver_later if self.for_tiers?
     end
     send_dossier_decision_to_experts(self)
     log_dossier_operation(instructeur, :accepter, self)
@@ -1036,6 +1040,7 @@ def after_accepter_automatiquement
     remove_titres_identite!
     MailTemplatePresenterService.create_commentaire_for_state(self)
     NotificationMailer.send_accepte_notification(self).deliver_later
+    NotificationMailer.send_notification_for_tiers(self).deliver_later if self.for_tiers?
     log_automatic_dossier_operation(:accepter, self)
   end
 
@@ -1061,6 +1066,7 @@ def after_refuser(h)
 
     if !disable_notification
       NotificationMailer.send_refuse_notification(self).deliver_later
+      NotificationMailer.send_notification_for_tiers(self).deliver_later if self.for_tiers?
     end
     send_dossier_decision_to_experts(self)
     log_dossier_operation(instructeur, :refuser, self)
@@ -1080,6 +1086,7 @@ def after_refuser_automatiquement
     remove_titres_identite!
     MailTemplatePresenterService.create_commentaire_for_state(self)
     NotificationMailer.send_refuse_notification(self).deliver_later
+    NotificationMailer.send_notification_for_tiers(self).deliver_later if self.for_tiers?
     log_automatic_dossier_operation(:refuser, self)
   end
 
@@ -1105,6 +1112,7 @@ def after_classer_sans_suite(h)
 
     if !disable_notification
       NotificationMailer.send_sans_suite_notification(self).deliver_later
+      NotificationMailer.send_notification_for_tiers(self).deliver_later if self.for_tiers?
     end
     send_dossier_decision_to_experts(self)
     log_dossier_operation(instructeur, :classer_sans_suite, self)
diff --git a/app/views/notification_mailer/send_notification_for_tiers.html.haml b/app/views/notification_mailer/send_notification_for_tiers.html.haml
new file mode 100644
index 00000000000..aa839fa2ab4
--- /dev/null
+++ b/app/views/notification_mailer/send_notification_for_tiers.html.haml
@@ -0,0 +1,17 @@
+- content_for :procedure_logo do
+  = render 'layouts/mailers/logo', url: @logo_url
+
+%p
+  Bonjour,
+
+%p= "#{ t("instructeurs.dossiers.decisions_rendues_block.without_email.#{@dossier.state}", processed_at: l(@dossier.updated_at.to_date))}."
+
+%p= "Le dossier nº #{@dossier.id} est rempli en votre nom par le mandataire #{@dossier.mandataire_first_name} #{@dossier.mandataire_last_name} sur la procédure #{@dossier.procedure.libelle}."
+
+%p= "Pour en savoir plus, veuillez-vous rapprocher du mandataire #{@dossier.user.email}."
+
+%p
+  = t(:best_regards, scope: [:views, :shared, :greetings])
+  %br
+    = t('layouts.mailers.signature.team')
+    #{APPLICATION_NAME.gsub(".","&#8288;.").html_safe}
diff --git a/spec/controllers/instructeurs/dossiers_controller_spec.rb b/spec/controllers/instructeurs/dossiers_controller_spec.rb
index f76083a1981..406e6253e84 100644
--- a/spec/controllers/instructeurs/dossiers_controller_spec.rb
+++ b/spec/controllers/instructeurs/dossiers_controller_spec.rb
@@ -7,6 +7,8 @@
   let(:instructeurs) { [instructeur] }
   let(:procedure) { create(:procedure, :published, :for_individual, instructeurs: instructeurs) }
   let(:dossier) { create(:dossier, :en_construction, :with_individual, procedure: procedure) }
+  let(:dossier_for_tiers) { create(:dossier, :en_construction, :for_tiers_with_notification, procedure: procedure) }
+  let(:dossier_for_tiers_without_notif) { create(:dossier, :en_construction, :for_tiers_without_notification, procedure: procedure) }
   let(:fake_justificatif) { fixture_file_upload('spec/fixtures/files/piece_justificative_0.pdf', 'application/pdf') }
 
   before { sign_in(instructeur.user) }
@@ -333,6 +335,58 @@
       end
     end
 
+    context "with for_tiers" do
+      before do
+        dossier_for_tiers.passer_en_instruction!(instructeur: instructeur)
+        sign_in(instructeur.user)
+      end
+      context 'without continuation' do
+        subject { post :terminer, params: { process_action: "classer_sans_suite", procedure_id: procedure.id, dossier_id: dossier_for_tiers.id }, format: :turbo_stream }
+
+        it 'Notification email is sent' do
+          expect(NotificationMailer).to receive(:send_sans_suite_notification)
+            .with(dossier_for_tiers).and_return(NotificationMailer)
+          expect(NotificationMailer).to receive(:deliver_later)
+
+          expect(NotificationMailer).to receive(:send_notification_for_tiers)
+            .with(dossier_for_tiers).and_return(NotificationMailer)
+          expect(NotificationMailer).to receive(:deliver_later)
+
+          subject
+        end
+
+        it '2 emails are sent' do
+          expect { perform_enqueued_jobs { subject } }.to change { ActionMailer::Base.deliveries.count }.by(2)
+        end
+      end
+    end
+
+    context "with for_tiers_without_notif" do
+      before do
+        dossier_for_tiers_without_notif.passer_en_instruction!(instructeur: instructeur)
+        sign_in(instructeur.user)
+      end
+      context 'without continuation' do
+        subject { post :terminer, params: { process_action: "classer_sans_suite", procedure_id: procedure.id, dossier_id: dossier_for_tiers_without_notif.id }, format: :turbo_stream }
+
+        it 'Notification email is sent' do
+          expect(NotificationMailer).to receive(:send_sans_suite_notification)
+            .with(dossier_for_tiers_without_notif).and_return(NotificationMailer)
+          expect(NotificationMailer).to receive(:deliver_later)
+
+          expect(NotificationMailer).to receive(:send_notification_for_tiers)
+            .with(dossier_for_tiers_without_notif).and_return(NotificationMailer)
+          expect(NotificationMailer).to receive(:deliver_later)
+
+          subject
+        end
+
+        it 'only one email is sent' do
+          expect { perform_enqueued_jobs { subject } }.to change { ActionMailer::Base.deliveries.count }.by(1)
+        end
+      end
+    end
+
     context "with classer_sans_suite" do
       before do
         dossier.passer_en_instruction!(instructeur: instructeur)
@@ -354,6 +408,9 @@
             .with(dossier).and_return(NotificationMailer)
           expect(NotificationMailer).to receive(:deliver_later)
 
+          expect(NotificationMailer).not_to receive(:send_notification_for_tiers)
+            .with(dossier)
+
           subject
         end
 
diff --git a/spec/factories/dossier.rb b/spec/factories/dossier.rb
index f6bf07516b8..f934364bf93 100644
--- a/spec/factories/dossier.rb
+++ b/spec/factories/dossier.rb
@@ -43,6 +43,40 @@
       end
     end
 
+    trait :for_tiers_with_notification do
+      for_tiers { true }
+      mandataire_first_name { 'John' }
+      mandataire_last_name { 'Doe' }
+
+      transient do
+        for_individual? { true }
+      end
+
+      after(:build) do |dossier, _evaluator|
+        if !dossier.procedure.for_individual?
+          raise 'Inconsistent factory: attempting to create a dossier :with_individual on a procedure that is not `for_individual?`'
+        end
+        dossier.individual = build(:individual, :with_notification, dossier: dossier)
+      end
+    end
+
+    trait :for_tiers_without_notification do
+      for_tiers { true }
+      mandataire_first_name { 'John' }
+      mandataire_last_name { 'Doe' }
+
+      transient do
+        for_individual? { true }
+      end
+
+      after(:build) do |dossier, _evaluator|
+        if !dossier.procedure.for_individual?
+          raise 'Inconsistent factory: attempting to create a dossier :with_individual on a procedure that is not `for_individual?`'
+        end
+        dossier.individual = build(:individual, :without_notification, dossier: dossier)
+      end
+    end
+
     trait :with_individual do
       transient do
         for_individual? { true }
diff --git a/spec/factories/individual.rb b/spec/factories/individual.rb
index c1aa66c5ddd..df00d814744 100644
--- a/spec/factories/individual.rb
+++ b/spec/factories/individual.rb
@@ -12,5 +12,14 @@
       prenom { nil }
       birthdate { nil }
     end
+
+    trait :with_notification do
+      notification_method { :email }
+      email { 'julien.xavier@test.com' }
+    end
+
+    trait :without_notification do
+      notification_method { :no_notification }
+    end
   end
 end
diff --git a/spec/mailers/previews/notification_mailer_preview.rb b/spec/mailers/previews/notification_mailer_preview.rb
index 04fdd078303..24b05836d25 100644
--- a/spec/mailers/previews/notification_mailer_preview.rb
+++ b/spec/mailers/previews/notification_mailer_preview.rb
@@ -19,6 +19,10 @@ def send_sans_suite_notification
     NotificationMailer.send_sans_suite_notification(dossier)
   end
 
+  def send_notification_for_tiers
+    NotificationMailer.send_notification_for_tiers(dossier)
+  end
+
   private
 
   def dossier