diff --git a/elections/migrations/0032_auto_20210820_0023.py b/elections/migrations/0032_auto_20210820_0023.py
new file mode 100644
index 0000000..d539a0b
--- /dev/null
+++ b/elections/migrations/0032_auto_20210820_0023.py
@@ -0,0 +1,29 @@
+# Generated by Django 3.2.6 on 2021-08-19 22:23
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("elections", "0031_alter_election_options"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="user",
+            name="has_valid_email",
+            field=models.BooleanField(
+                default=None, null=True, verbose_name="email valide"
+            ),
+        ),
+        migrations.AlterField(
+            model_name="election",
+            name="sent_mail",
+            field=models.BooleanField(
+                default=False,
+                null=True,
+                verbose_name="mail avec les identifiants envoyé",
+            ),
+        ),
+    ]
diff --git a/elections/models.py b/elections/models.py
index f99eda7..12593df 100644
--- a/elections/models.py
+++ b/elections/models.py
@@ -50,7 +50,7 @@ class Election(models.Model):
     )
 
     sent_mail = models.BooleanField(
-        _("mail avec les identifiants envoyé"), default=False
+        _("mail avec les identifiants envoyé"), null=True, default=False
     )
 
     created_by = models.ForeignKey(
@@ -232,6 +232,7 @@ class User(AbstractUser):
         on_delete=models.CASCADE,
     )
     full_name = models.CharField(_("Nom et Prénom"), max_length=150, blank=True)
+    has_valid_email = models.BooleanField(_("email valide"), null=True, default=None)
 
     @property
     def base_username(self):
diff --git a/elections/tasks.py b/elections/tasks.py
new file mode 100644
index 0000000..87e248f
--- /dev/null
+++ b/elections/tasks.py
@@ -0,0 +1,12 @@
+from background_task import background
+
+from .models import Election
+from .utils import send_mail
+
+
+@background(schedule=5)
+def send_election_mail(election_pk, subject, body, reply_to):
+    election = Election.objects.get(pk=election_pk)
+    send_mail(election, subject, body, reply_to)
+    election.sent_mail = True
+    election.save(update_fields=["sent_mail"])
diff --git a/elections/templates/elections/upload_voters.html b/elections/templates/elections/upload_voters.html
index a657596..63a9ef5 100644
--- a/elections/templates/elections/upload_voters.html
+++ b/elections/templates/elections/upload_voters.html
@@ -29,7 +29,7 @@
   </div>
 
   <div class="level-right">
-    {% if not election.sent_mail %}
+    {% if election.sent_mail is False %}
     <div class="level-item">
       <a class="button is-light is-outlined is-primary" href="{% url 'election.mail-voters' election.pk %}">
         <span class="icon">
@@ -38,6 +38,24 @@
         <span>{% trans "Envoyer le mail d'annonce" %}</span>
       </a>
     </div>
+    {% elif election.sent_mail is None %}
+    <div class="level-item">
+      <span class="button is-light is-outlined is-warning">
+        <span class="icon">
+          <i class="fas fa-sync-alt"></i>
+        </span>
+        <span>{% trans "Mail en cours de distribution" %}</span>
+      </span>
+    </div>
+    {% else %}
+    <div class="level-item">
+      <span class="button is-light is-outlined is-success">
+        <span class="icon">
+          <i class="fas fa-check"></i>
+        </span>
+        <span>{% trans "Mail envoyé" %}</span>
+      </span>
+    </div>
     {% endif %}
 
     <div class="level-item">
@@ -114,7 +132,18 @@
         <tr>
           <td>{{ v.base_username }}</td>
           <td>{{ v.full_name }}</td>
-          <td>{{ v.email }}</td>
+          <td>
+            {{ v.email }}
+            {% if v.has_valid_email %}
+            <span class="icon has-text-success is-pulled-right">
+              <i class="fas fa-check"></i>
+            </span>
+            {% elif v.has_valid_email is False %}
+            <span class="icon has-text-danger is-pulled-right">
+              <i class="fas fa-times"></i>
+            </span>
+            {% endif %}
+          </td>
         </tr>
         {% endfor %}
       </tbody>
diff --git a/elections/utils.py b/elections/utils.py
index 6e0eb5e..cd4facb 100644
--- a/elections/utils.py
+++ b/elections/utils.py
@@ -1,5 +1,6 @@
 import csv
 import io
+import smtplib
 
 import networkx as nx
 import numpy as np
@@ -8,7 +9,7 @@ from networkx.algorithms.dag import ancestors, descendants
 from django.contrib.auth import get_user_model
 from django.contrib.auth.hashers import make_password
 from django.core.exceptions import ValidationError
-from django.core.mail import EmailMessage  # , get_connection
+from django.core.mail import EmailMessage
 from django.core.validators import validate_email
 from django.template.loader import render_to_string
 from django.urls import reverse
@@ -383,13 +384,14 @@ def check_csv(csv_file):
     return errors
 
 
-def send_mail(election, mail_form):
+def send_mail(election, subject, body, reply_to):
     """Envoie le mail d'annonce de l'élection avec identifiants et mot de passe
     aux votant·e·s, le mdp est généré en même temps que le mail est envoyé.
     """
     User = get_user_model()
 
-    voters = list(election.registered_voters.all())
+    # On n'envoie le mail qu'aux personnes qui n'en n'ont pas déjà reçu un
+    voters = list(election.registered_voters.exclude(has_valid_email=True))
     e_url = reverse("election.view", args=[election.id])
     url = f"https://vote.eleves.ens.fr{e_url}"
     messages = []
@@ -397,18 +399,28 @@ def send_mail(election, mail_form):
         password = generate_password()
         v.password = make_password(password)
         messages.append(
-            EmailMessage(
-                subject=mail_form.cleaned_data["objet"],
-                body=mail_form.cleaned_data["message"].format(
-                    full_name=v.full_name,
-                    election_url=url,
-                    username=v.base_username,
-                    password=password,
+            (
+                EmailMessage(
+                    subject=subject,
+                    body=body.format(
+                        full_name=v.full_name,
+                        election_url=url,
+                        username=v.base_username,
+                        password=password,
+                    ),
+                    to=[v.email],
+                    reply_to=[reply_to],
                 ),
-                to=[v.email],
+                v,
             )
         )
-    # get_connection(fail_silently=False).send_messages(messages)
-    for m in messages:
-        m.send()
-    User.objects.bulk_update(voters, ["password"])
+
+    for (m, v) in messages:
+        try:
+            m.send()
+        except smtplib.SMTPException:
+            v.has_valid_email = False
+        else:
+            v.has_valid_email = True
+
+    User.objects.bulk_update(voters, ["password", "has_valid_email"])
diff --git a/elections/views.py b/elections/views.py
index 24cf3cb..5e9d748 100644
--- a/elections/views.py
+++ b/elections/views.py
@@ -41,7 +41,8 @@ from .mixins import (
 )
 from .models import Election, Option, Question, Vote
 from .staticdefs import MAIL_VOTE_DELETED, MAIL_VOTERS, QUESTION_TYPES, VOTE_RULES
-from .utils import create_users, send_mail
+from .tasks import send_election_mail
+from .utils import create_users
 
 User = get_user_model()
 
@@ -158,7 +159,7 @@ class ElectionUploadVotersView(CreatorOnlyEditMixin, SuccessMessageMixin, FormVi
 class ElectionMailVotersView(CreatorOnlyEditMixin, SuccessMessageMixin, FormView):
     model = Election
     form_class = VoterMailForm
-    success_message = _("Mail d'annonce envoyé avec succès !")
+    success_message = _("Mail d'annonce en cours d'envoi !")
     template_name = "elections/mail_voters.html"
 
     def get_queryset(self):
@@ -181,9 +182,14 @@ class ElectionMailVotersView(CreatorOnlyEditMixin, SuccessMessageMixin, FormView
         return super().post(request, *args, **kwargs)
 
     def form_valid(self, form):
-        self.object.sent_mail = True
-        send_mail(self.object, form)
+        self.object.sent_mail = None
         self.object.save()
+        send_election_mail(
+            election_pk=self.object.pk,
+            subject=form.cleaned_data["objet"],
+            body=form.cleaned_data["message"],
+            reply_to=self.request.user.email,
+        )
         return super().form_valid(form)
 
 
diff --git a/kadenios/settings/common.py b/kadenios/settings/common.py
index 6143d80..e15dd35 100644
--- a/kadenios/settings/common.py
+++ b/kadenios/settings/common.py
@@ -53,6 +53,7 @@ INSTALLED_APPS = [
     "django.contrib.sessions",
     "django.contrib.messages",
     "kadenios.apps.IgnoreSrcStaticFilesConfig",
+    "background_task",
     "shared",
     "elections",
     "faqs",
diff --git a/requirements.txt b/requirements.txt
index bc3ab09..a332359 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,7 +1,8 @@
 django==3.2.*
-django-translated-fields==0.11.1
+django-translated-fields==0.11.*
 authens>=0.1b2
 markdown
 numpy
 networkx
 python-csv
+django-background-tasks