diff --git a/src/paperless/settings/__init__.py b/src/paperless/settings/__init__.py
index 7cd504af1..6b400963b 100644
--- a/src/paperless/settings/__init__.py
+++ b/src/paperless/settings/__init__.py
@@ -705,6 +705,12 @@ CELERY_BROKER_TRANSPORT_OPTIONS = {
 CELERY_TASK_TRACK_STARTED = True
 CELERY_TASK_TIME_LIMIT: Final[int] = get_int_from_env("PAPERLESS_WORKER_TIMEOUT", 1800)
 
+# https://docs.celeryq.dev/en/stable/userguide/configuration.html#std-setting-task_allow_error_cb_on_chord_header
+# Without this, a failing chord header never triggers the errback, so a mail
+# whose attachments all fail is never recorded and is re-fetched forever.
+# The errback runs once per failed header task, so it must be idempotent.
+CELERY_TASK_ALLOW_ERROR_CB_ON_CHORD_HEADER = True
+
 CELERY_CACHE_BACKEND = "default"
 
 # https://docs.celeryq.dev/en/stable/userguide/configuration.html#task-serializer
diff --git a/src/paperless_mail/mail.py b/src/paperless_mail/mail.py
index 0af5eb9c7..5f7e29561 100644
--- a/src/paperless_mail/mail.py
+++ b/src/paperless_mail/mail.py
@@ -334,18 +334,24 @@ def error_callback(
     """
     A shared task that is called whenever something goes wrong during
     consumption of a file. See queue_consumption_tasks.
+
+    With CELERY_TASK_ALLOW_ERROR_CB_ON_CHORD_HEADER enabled this runs once per
+    failed header task, not once per chord, so it must be idempotent.
     """
     rule = MailRule.objects.get(pk=rule_id)
+    received = make_aware(message_date) if is_naive(message_date) else message_date
 
-    ProcessedMail.objects.create(
+    ProcessedMail.objects.get_or_create(
         rule=rule,
         folder=rule.folder,
         uid=message_uid,
         uid_validity=uid_validity,
-        subject=message_subject,
-        received=make_aware(message_date) if is_naive(message_date) else message_date,
-        status="FAILED",
-        error=traceback.format_exc(),
+        defaults={
+            "subject": message_subject,
+            "received": received,
+            "status": "FAILED",
+            "error": traceback.format_exc(),
+        },
     )
 
 
diff --git a/src/paperless_mail/tests/test_mail.py b/src/paperless_mail/tests/test_mail.py
index f0183c1f5..bba505175 100644
--- a/src/paperless_mail/tests/test_mail.py
+++ b/src/paperless_mail/tests/test_mail.py
@@ -36,6 +36,7 @@ from paperless_mail.mail import MailAccountHandler
 from paperless_mail.mail import MailError
 from paperless_mail.mail import TagMailAction
 from paperless_mail.mail import apply_mail_action
+from paperless_mail.mail import error_callback
 from paperless_mail.mail import get_mailbox
 from paperless_mail.models import MailAccount
 from paperless_mail.models import MailRule
@@ -2045,6 +2046,44 @@ class TestPostConsumeAction(TestCase):
         self.assertIn("Test Exception", processed_mail.error)
 
 
+@pytest.mark.django_db
+class TestErrorCallback:
+    def test_error_callback_is_idempotent_for_same_mail(self) -> None:
+        """
+        GIVEN:
+            - A mail rule and a mail that failed to be consumed
+        WHEN:
+            - error_callback is invoked more than once for the same mail, as
+              happens when task_allow_error_cb_on_chord_header fires the
+              errback once per failed header task in a chord
+        THEN:
+            - Only one ProcessedMail row is created for that mail
+        """
+        rule = MailRuleFactory()
+        message_uid = "12345"
+
+        for _ in range(2):
+            error_callback(
+                None,
+                Exception("Test Exception"),
+                None,
+                rule_id=rule.pk,
+                message_uid=message_uid,
+                message_subject="Test Subject",
+                message_date=timezone.make_aware(
+                    timezone.datetime(2023, 1, 1, 12, 0, 0),
+                ),
+            )
+
+        processed_mails = ProcessedMail.objects.filter(
+            rule=rule,
+            uid=message_uid,
+            folder=rule.folder,
+        )
+        assert processed_mails.count() == 1
+        assert processed_mails.get().status == "FAILED"
+
+
 class TestManagementCommand(TestCase):
     @mock.patch(
         "paperless_mail.management.commands.mail_fetcher.tasks.process_mail_accounts",