diff --git a/CHANGELOG.md b/CHANGELOG.md
index c0544d166..3ebea00dd 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,7 @@ and this project adheres to
 
 ### Added
 
+- ✨(dimail) send pending mailboxes upon domain activation
 - 🧑‍💻(oidc) add ability to pull registration ID (e.g. SIRET) from OIDC #577
 
 ### Fixed
diff --git a/src/backend/mailbox_manager/api/client/serializers.py b/src/backend/mailbox_manager/api/client/serializers.py
index 9de76208b..98de70de6 100644
--- a/src/backend/mailbox_manager/api/client/serializers.py
+++ b/src/backend/mailbox_manager/api/client/serializers.py
@@ -43,7 +43,7 @@ def create(self, validated_data):
                 validated_data, self.context["request"].user.sub
             )
 
-            # fix format to have actual json, and remove uuid
+            # fix format to have actual json
             mailbox_data = json.loads(
                 response.content.decode("utf-8").replace("'", '"')
             )
diff --git a/src/backend/mailbox_manager/tests/test_utils_dimail_client.py b/src/backend/mailbox_manager/tests/test_utils_dimail_client.py
index 970cdaa0e..b9392ce0a 100644
--- a/src/backend/mailbox_manager/tests/test_utils_dimail_client.py
+++ b/src/backend/mailbox_manager/tests/test_utils_dimail_client.py
@@ -12,6 +12,8 @@
 import responses
 from rest_framework import status
 
+from core import factories as core_factories
+
 from mailbox_manager import enums, factories, models
 from mailbox_manager.utils.dimail import DimailAPIClient
 
@@ -20,6 +22,12 @@
 pytestmark = pytest.mark.django_db
 
 
+@pytest.fixture
+def authenticated_user():
+    """Create an user"""
+    return core_factories.UserFactory()
+
+
 def test_dimail_synchronization__already_sync():
     """
     No mailbox should be created when everything is already synced.
@@ -176,3 +184,21 @@ def test_dimail__fetch_domain_status_from_dimail():
         response = dimail_client.fetch_domain_status(domain)
         assert response.status_code == status.HTTP_200_OK
         assert domain.status == enums.MailDomainStatusChoices.FAILED
+
+
+def test_dimail___pending_mailboxes_enabled_upon_domain_activation(caplog):
+    """Status of pending mailboxes should switch to "enabled" when their related domain
+    goes from "pending" to "enabled"."""
+
+    domain = factories.MailDomainFactory()
+    factories.MailboxFactory.create_batch(
+        3, domain=domain, status=enums.MailboxStatusChoices.PENDING
+    )
+
+    dimail_client = DimailAPIClient()
+    dimail_client.enable_pending_mailboxes(domain=domain)
+
+    mailboxes = models.Mailbox.objects.filter(domain=domain)
+    assert len(mailboxes) == 3
+    for mailbox in mailboxes:
+        assert mailbox.status == enums.MailboxStatusChoices.ENABLED
diff --git a/src/backend/mailbox_manager/utils/dimail.py b/src/backend/mailbox_manager/utils/dimail.py
index c4ec5f4fb..507ab557b 100644
--- a/src/backend/mailbox_manager/utils/dimail.py
+++ b/src/backend/mailbox_manager/utils/dimail.py
@@ -138,6 +138,9 @@ def create_mailbox(self, mailbox, user_sub=None):
             )
             raise error
 
+        import pdb
+
+        pdb.set_trace()
         if response.status_code == status.HTTP_201_CREATED:
             logger.info(
                 "Mailbox successfully created on domain %s by user %s",
@@ -420,3 +423,30 @@ def fetch_domain_status(self, domain):
                 domain.save()
             return response
         return self.raise_exception_for_unexpected_response(response)
+
+    def enable_pending_mailboxes(self, domain):
+        """Send request for all pending mailboxes of a domain."""
+
+        pending_mailboxes = models.Mailbox.objects.filter(
+            domain=domain, status=enums.MailboxStatusChoices.PENDING
+        )
+        for mailbox in pending_mailboxes:
+            from mailbox_manager.api.client import serializers
+
+            serialized_mailbox = serializers.MailboxSerializer(mailbox).data
+            serialized_mailbox["domain"] = domain
+
+            response = self.create_mailbox(serialized_mailbox)
+
+            # fix format to have actual json
+            mailbox_data = json.loads(
+                response.content.decode("utf-8").replace("'", '"')
+            )
+            mailbox.status = enums.MailDomainStatusChoices.ENABLED
+            mailbox.save()
+
+            # send confirmation email
+            self.notify_mailbox_creation(
+                recipient=serialized_mailbox["secondary_email"], mailbox_data=mailbox_data
+            )
+