diff --git a/app/controllers/new_gestionnaire/avis_controller.rb b/app/controllers/new_gestionnaire/avis_controller.rb
index 07367a7fd..3fd9b2376 100644
--- a/app/controllers/new_gestionnaire/avis_controller.rb
+++ b/app/controllers/new_gestionnaire/avis_controller.rb
@@ -3,7 +3,7 @@ module NewGestionnaire
     before_action :authenticate_gestionnaire!, except: [:sign_up, :create_gestionnaire]
     before_action :redirect_if_no_sign_up_needed, only: [:sign_up]
     before_action :check_avis_exists_and_email_belongs_to_avis, only: [:sign_up, :create_gestionnaire]
-    before_action :set_avis_and_dossier, only: [:show, :instruction, :messagerie, :create_commentaire]
+    before_action :set_avis_and_dossier, only: [:show, :instruction, :messagerie, :create_commentaire, :update]
 
     A_DONNER_STATUS = 'a-donner'
     DONNES_STATUS   = 'donnes'
@@ -29,12 +29,18 @@ module NewGestionnaire
     end
 
     def instruction
+      @new_avis = Avis.new
     end
 
     def update
-      avis.update(avis_params)
-      flash.notice = 'Votre réponse est enregistrée.'
-      redirect_to instruction_gestionnaire_avis_path(avis)
+      if @avis.update(avis_params)
+        flash.notice = 'Votre réponse est enregistrée.'
+        redirect_to instruction_gestionnaire_avis_path(@avis)
+      else
+        flash.now.alert = @avis.errors.full_messages
+        @new_avis = Avis.new
+        render :instruction
+      end
     end
 
     def messagerie
@@ -55,8 +61,16 @@ module NewGestionnaire
 
     def create_avis
       confidentiel = avis.confidentiel || params[:avis][:confidentiel]
-      Avis.create(create_avis_params.merge(claimant: current_gestionnaire, dossier: avis.dossier, confidentiel: confidentiel))
-      redirect_to instruction_gestionnaire_avis_path(avis)
+      @new_avis = Avis.new(create_avis_params.merge(claimant: current_gestionnaire, dossier: avis.dossier, confidentiel: confidentiel))
+
+      if @new_avis.save
+        flash.notice = "Une demande d'avis a été envoyée à #{@new_avis.email_to_display}"
+        redirect_to instruction_gestionnaire_avis_path(avis)
+      else
+        flash.now.alert = @new_avis.errors.full_messages
+        set_avis_and_dossier
+        render :instruction
+      end
     end
 
     def sign_up
diff --git a/app/controllers/new_gestionnaire/dossiers_controller.rb b/app/controllers/new_gestionnaire/dossiers_controller.rb
index c91e0d2b5..e978a348c 100644
--- a/app/controllers/new_gestionnaire/dossiers_controller.rb
+++ b/app/controllers/new_gestionnaire/dossiers_controller.rb
@@ -27,6 +27,7 @@ module NewGestionnaire
 
     def avis
       @avis_seen_at = current_gestionnaire.follows.find_by(dossier: dossier)&.avis_seen_at
+      @avis = Avis.new
     end
 
     def personnes_impliquees
@@ -159,8 +160,15 @@ module NewGestionnaire
     end
 
     def create_avis
-      Avis.create(avis_params.merge(claimant: current_gestionnaire, dossier: dossier))
-      redirect_to avis_gestionnaire_dossier_path(procedure, dossier)
+      @avis = Avis.new(avis_params.merge(claimant: current_gestionnaire, dossier: dossier))
+      if @avis.save
+        flash.notice = "Une demande d'avis a été envoyée à #{@avis.email_to_display}"
+        redirect_to avis_gestionnaire_dossier_path(procedure, dossier)
+      else
+        flash.now.alert = @avis.errors.full_messages
+        @avis_seen_at = current_gestionnaire.follows.find_by(dossier: dossier)&.avis_seen_at
+        render :avis
+      end
     end
 
     def update_annotations
diff --git a/app/models/administrateur.rb b/app/models/administrateur.rb
index ffd21bd17..94c0498f0 100644
--- a/app/models/administrateur.rb
+++ b/app/models/administrateur.rb
@@ -1,14 +1,16 @@
 class Administrateur < ApplicationRecord
+  include CredentialsSyncableConcern
+  include EmailSanitizableConcern
+
   devise :database_authenticatable, :registerable,
     :recoverable, :rememberable, :trackable, :validatable
 
   has_and_belongs_to_many :gestionnaires
   has_many :procedures
 
+  before_validation -> { sanitize_email(:email) }
   before_save :ensure_api_token
 
-  include CredentialsSyncableConcern
-
   scope :inactive, -> { where(active: false) }
 
   def self.find_inactive_by_token(reset_password_token)
diff --git a/app/models/avis.rb b/app/models/avis.rb
index e6d78c580..108d24777 100644
--- a/app/models/avis.rb
+++ b/app/models/avis.rb
@@ -1,9 +1,13 @@
 class Avis < ApplicationRecord
+  include EmailSanitizableConcern
+
   belongs_to :dossier, touch: true
   belongs_to :gestionnaire
   belongs_to :claimant, class_name: 'Gestionnaire'
 
-  before_save :clean_email
+  validates :email, format: { with: Devise.email_regexp, message: "n'est pas valide" }, allow_nil: true
+
+  before_validation -> { sanitize_email(:email) }
   before_create :try_to_assign_gestionnaire
   after_create :notify_gestionnaire
 
@@ -29,12 +33,6 @@ class Avis < ApplicationRecord
 
   private
 
-  def clean_email
-    if email.present?
-      self.email = email.downcase.strip
-    end
-  end
-
   def notify_gestionnaire
     AvisMailer.avis_invitation(self).deliver_now
   end
diff --git a/app/models/concerns/email_sanitizable_concern.rb b/app/models/concerns/email_sanitizable_concern.rb
new file mode 100644
index 000000000..d6c715815
--- /dev/null
+++ b/app/models/concerns/email_sanitizable_concern.rb
@@ -0,0 +1,10 @@
+module EmailSanitizableConcern
+  extend ActiveSupport::Concern
+
+  def sanitize_email(attribute)
+    value_to_sanitize = self.send(attribute)
+    if value_to_sanitize.present?
+      self[attribute] = value_to_sanitize.gsub(/[[:space:]]/, ' ').strip.downcase
+    end
+  end
+end
diff --git a/app/models/gestionnaire.rb b/app/models/gestionnaire.rb
index a01eddad9..6fc42851d 100644
--- a/app/models/gestionnaire.rb
+++ b/app/models/gestionnaire.rb
@@ -1,9 +1,14 @@
 class Gestionnaire < ApplicationRecord
+  include CredentialsSyncableConcern
+  include EmailSanitizableConcern
+
   devise :database_authenticatable, :registerable,
     :recoverable, :rememberable, :trackable, :validatable
 
   has_and_belongs_to_many :administrateurs
 
+  before_validation -> { sanitize_email(:email) }
+
   has_many :assign_to, dependent: :destroy
   has_many :procedures, through: :assign_to
   has_many :dossiers, -> { state_not_brouillon }, through: :procedures
@@ -12,8 +17,6 @@ class Gestionnaire < ApplicationRecord
   has_many :avis
   has_many :dossiers_from_avis, through: :avis, source: :dossier
 
-  include CredentialsSyncableConcern
-
   def visible_procedures
     procedures.publiees_ou_archivees
   end
diff --git a/app/models/invite.rb b/app/models/invite.rb
index 526026634..3abb44e39 100644
--- a/app/models/invite.rb
+++ b/app/models/invite.rb
@@ -1,9 +1,13 @@
 class Invite < ApplicationRecord
+  include EmailSanitizableConcern
+
   belongs_to :dossier
   belongs_to :user
 
+  before_validation -> { sanitize_email(:email) }
+
   validates :email, presence: true
   validates :email, uniqueness: { scope: :dossier_id }
 
-  validates :email, email_format: true
+  validates :email, format: { with: Devise.email_regexp, message: "n'est pas valide" }, allow_nil: true
 end
diff --git a/app/models/user.rb b/app/models/user.rb
index a495d2f84..83c030beb 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -1,4 +1,7 @@
 class User < ApplicationRecord
+  include CredentialsSyncableConcern
+  include EmailSanitizableConcern
+
   enum loged_in_with_france_connect: {
     particulier: 'particulier',
     entreprise: 'entreprise'
@@ -18,7 +21,7 @@ class User < ApplicationRecord
   delegate :given_name, :family_name, :email_france_connect, :gender, :birthdate, :birthplace, :france_connect_particulier_id, to: :france_connect_information
   accepts_nested_attributes_for :france_connect_information
 
-  include CredentialsSyncableConcern
+  before_validation -> { sanitize_email(:email) }
 
   def self.find_for_france_connect email, siret
     user = User.find_by(email: email)
diff --git a/app/validators/email_format_validator.rb b/app/validators/email_format_validator.rb
deleted file mode 100644
index f9bd0d76d..000000000
--- a/app/validators/email_format_validator.rb
+++ /dev/null
@@ -1,10 +0,0 @@
-class EmailFormatValidator < ActiveModel::Validator
-  def email_regex
-    /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\z/i
-  end
-
-  def validate(record)
-    return if record.email.blank?
-    record.errors[:base] << "Email invalide" if !email_regex.match(record.email)
-  end
-end
diff --git a/app/views/new_gestionnaire/avis/instruction.html.haml b/app/views/new_gestionnaire/avis/instruction.html.haml
index 943764c97..1ff164457 100644
--- a/app/views/new_gestionnaire/avis/instruction.html.haml
+++ b/app/views/new_gestionnaire/avis/instruction.html.haml
@@ -21,6 +21,6 @@
         .send-wrapper
           = f.submit 'Envoyer votre avis', class: 'button send'
 
-  = render partial: "new_gestionnaire/shared/avis/form", locals: { url: avis_gestionnaire_avis_path(@avis), must_be_confidentiel: @avis.confidentiel? }
+  = render partial: "new_gestionnaire/shared/avis/form", locals: { url: avis_gestionnaire_avis_path(@avis), must_be_confidentiel: @avis.confidentiel?, avis: @new_avis }
 
   = render partial: 'new_gestionnaire/shared/avis/list', locals: { avis: @dossier.avis_for(current_gestionnaire), avis_seen_at: nil }
diff --git a/app/views/new_gestionnaire/dossiers/avis.html.haml b/app/views/new_gestionnaire/dossiers/avis.html.haml
index 87ce6b25a..67881abbb 100644
--- a/app/views/new_gestionnaire/dossiers/avis.html.haml
+++ b/app/views/new_gestionnaire/dossiers/avis.html.haml
@@ -3,6 +3,6 @@
 = render partial: "header", locals: { dossier: @dossier }
 
 .container
-  = render partial: "new_gestionnaire/shared/avis/form", locals: { url: avis_gestionnaire_dossier_path(@dossier.procedure, @dossier), must_be_confidentiel: false }
+  = render partial: "new_gestionnaire/shared/avis/form", locals: { url: avis_gestionnaire_dossier_path(@dossier.procedure, @dossier), must_be_confidentiel: false, avis: @avis }
 
   = render partial: 'new_gestionnaire/shared/avis/list', locals: { avis: @dossier.avis, avis_seen_at: @avis_seen_at }
diff --git a/app/views/new_gestionnaire/shared/avis/_form.html.haml b/app/views/new_gestionnaire/shared/avis/_form.html.haml
index 66e2cfe55..2a660ce51 100644
--- a/app/views/new_gestionnaire/shared/avis/_form.html.haml
+++ b/app/views/new_gestionnaire/shared/avis/_form.html.haml
@@ -2,9 +2,9 @@
   %h1.tab-title Inviter une personne à donner son avis
   %p.avis-notice L'invité pourra consulter, donner un avis sur le dossier et contribuer au fil de messagerie, mais il ne pourra le modifier.
 
-  = form_for Avis.new, url: url, html: { class: 'form' } do |f|
+  = form_for avis, url: url, html: { class: 'form' } do |f|
     = f.email_field :email, placeholder: 'Adresse email', required: true
-    = f.text_area :introduction, rows: 3, value: 'Bonjour, merci de me donner votre avis sur ce dossier.', required: true
+    = f.text_area :introduction, rows: 3, value: avis.introduction || 'Bonjour, merci de me donner votre avis sur ce dossier.', required: true
     .flex.justify-between.align-baseline
       - if must_be_confidentiel
         %p.confidentiel.flex
diff --git a/config/locales/models/avis/fr.yml b/config/locales/models/avis/fr.yml
new file mode 100644
index 000000000..9d1c31792
--- /dev/null
+++ b/config/locales/models/avis/fr.yml
@@ -0,0 +1,7 @@
+fr:
+  activerecord:
+    models:
+      avis: 'Avis'
+    attributes:
+      avis:
+        answer: "Réponse"
diff --git a/spec/controllers/new_gestionnaire/avis_controller_spec.rb b/spec/controllers/new_gestionnaire/avis_controller_spec.rb
index c34f1ed79..e1bb89021 100644
--- a/spec/controllers/new_gestionnaire/avis_controller_spec.rb
+++ b/spec/controllers/new_gestionnaire/avis_controller_spec.rb
@@ -108,6 +108,16 @@ describe NewGestionnaire::AvisController, type: :controller do
         post :create_avis, params: { id: previous_avis.id, avis: { email: email, introduction: intro, confidentiel: asked_confidentiel } }
       end
 
+      context 'when an invalid email' do
+        let(:previous_avis_confidentiel) { false }
+        let(:asked_confidentiel) { false }
+        let(:email) { "toto.fr" }
+
+        it { expect(response).to render_template :instruction }
+        it { expect(flash.alert).to eq(["Email n'est pas valide"]) }
+        it { expect(Avis.last).to eq(previous_avis) }
+      end
+
       context 'when the previous avis is public' do
         let(:previous_avis_confidentiel) { false }
 
diff --git a/spec/controllers/new_gestionnaire/dossiers_controller_spec.rb b/spec/controllers/new_gestionnaire/dossiers_controller_spec.rb
index 6f8c67cb4..2c4622bfe 100644
--- a/spec/controllers/new_gestionnaire/dossiers_controller_spec.rb
+++ b/spec/controllers/new_gestionnaire/dossiers_controller_spec.rb
@@ -337,20 +337,34 @@ describe NewGestionnaire::DossiersController, type: :controller do
   describe "#create_avis" do
     let(:saved_avis) { dossier.avis.first }
 
-    before do
+    subject do
       post :create_avis, params: {
         procedure_id: procedure.id,
         dossier_id: dossier.id,
-        avis: { email: 'email@a.com', introduction: 'intro', confidentiel: true }
+        avis: { email: email, introduction: 'intro', confidentiel: true }
       }
     end
 
+    before do
+      subject
+    end
+
+    let(:email) { 'email@a.com' }
+
     it { expect(saved_avis.email).to eq('email@a.com') }
     it { expect(saved_avis.introduction).to eq('intro') }
     it { expect(saved_avis.confidentiel).to eq(true) }
     it { expect(saved_avis.dossier).to eq(dossier) }
     it { expect(saved_avis.claimant).to eq(gestionnaire) }
     it { expect(response).to redirect_to(avis_gestionnaire_dossier_path(dossier.procedure, dossier)) }
+
+    context "with an invalid email" do
+      let(:email) { 'emaila.com' }
+
+      it { expect(response).to render_template :avis }
+      it { expect(flash.alert).to eq(["Email n'est pas valide"]) }
+      it { expect { subject }.not_to change(Avis, :count) }
+    end
   end
 
   describe "#update_annotations" do
diff --git a/spec/models/avis_spec.rb b/spec/models/avis_spec.rb
index 3ca680440..0cce41b9c 100644
--- a/spec/models/avis_spec.rb
+++ b/spec/models/avis_spec.rb
@@ -118,7 +118,7 @@ RSpec.describe Avis, type: :model do
     end
   end
 
-  describe "#clean_email" do
+  describe "email sanitization" do
     subject { Avis.create(claimant: claimant, email: email, dossier: create(:dossier), gestionnaire: create(:gestionnaire)) }
 
     context "when there is no email" do
diff --git a/spec/models/concern/email_sanitizable_concern_spec.rb b/spec/models/concern/email_sanitizable_concern_spec.rb
new file mode 100644
index 000000000..7b98b7d82
--- /dev/null
+++ b/spec/models/concern/email_sanitizable_concern_spec.rb
@@ -0,0 +1,51 @@
+describe EmailSanitizableConcern, type: :model do
+  describe 'sanitize_email' do
+    let(:email_concern) do
+      (Class.new do
+         include EmailSanitizableConcern
+         attr_accessor :email
+
+         def initialize(email)
+           self.email = email
+         end
+
+         def [](key)
+           self.send(key)
+         end
+
+         def []=(key, value)
+           self.send("#{key}=", value)
+         end
+       end).new(email)
+    end
+
+    before do
+      email_concern.sanitize_email(:email)
+    end
+
+    context 'on an empty email' do
+      let(:email) { '' }
+      it { expect(email_concern.email).to eq('') }
+    end
+
+    context 'on a valid email' do
+      let(:email) { 'michel@toto.fr' }
+      it { expect(email_concern.email).to eq('michel@toto.fr') }
+    end
+
+    context 'on an email with trailing spaces' do
+      let(:email) { ' michel@toto.fr    ' }
+      it { expect(email_concern.email).to eq('michel@toto.fr') }
+    end
+
+    context 'on an email with trailing nbsp' do
+      let(:email) { ' michel@toto.fr  ' }
+      it { expect(email_concern.email).to eq('michel@toto.fr') }
+    end
+
+    context 'on an invalid email' do
+      let(:email) { 'mich el@toto.fr' }
+      it { expect(email_concern.email).to eq('mich el@toto.fr') }
+    end
+  end
+end
diff --git a/spec/models/invite_spec.rb b/spec/models/invite_spec.rb
index 63978930d..e952df95d 100644
--- a/spec/models/invite_spec.rb
+++ b/spec/models/invite_spec.rb
@@ -24,5 +24,36 @@ describe Invite do
 
       it { expect{ subject }.to raise_error ActiveRecord::RecordInvalid }
     end
+
+    context "email validation" do
+      let(:invite) { build(:invite, email: email, dossier: dossier1) }
+
+      context 'when an email is invalid' do
+        let(:email) { 'toto.fr' }
+
+        it do
+          expect(invite.save).to be false
+          expect(invite.errors.full_messages).to eq(["Email n'est pas valide"])
+        end
+
+        context 'when an email is empty' do
+          let(:email) { nil }
+
+          it do
+            expect(invite.save).to be false
+            expect(invite.errors.full_messages).to eq(["Email est vide"])
+          end
+        end
+      end
+
+      context 'when an email is valid' do
+        let(:email) { 'toto@toto.fr' }
+
+        it do
+          expect(invite.save).to be true
+          expect(invite.errors.full_messages).to eq([])
+        end
+      end
+    end
   end
 end