diff --git a/crm_request/models/request.py b/crm_request/models/request.py
index 201741dc9..b473c1fb8 100644
--- a/crm_request/models/request.py
+++ b/crm_request/models/request.py
@@ -220,7 +220,12 @@ def message_new(self, msg, custom_values=None):
         defaults.pop("name", False)
         defaults.update(custom_values)
 
-        request_id = super().message_new(msg, defaults)
+        # The responsible set by the e-mail alias follows the request and gets
+        # the incoming e-mail itself: no separate "You have been assigned"
+        # e-mail on top of it (T3647). Assigning by hand still sends it.
+        request_id = super(
+            CrmClaim, self.with_context(mail_auto_subscribe_no_notify=True)
+        ).message_new(msg, defaults)
         request = self.browse(request_id.id)
         if not request.language:
             request.language = (
@@ -234,7 +239,7 @@ def message_new(self, msg, custom_values=None):
         except Exception as e:
             _logger.error(f"The automatic mail failed\n{e}")
 
-        return request_id
+        return request
 
     def message_update(self, msg_dict, update_vals=None):
         """Change the stage to "Waiting on support" when the customer writes a
diff --git a/crm_request/tests/__init__.py b/crm_request/tests/__init__.py
index da65f0539..91f23880f 100644
--- a/crm_request/tests/__init__.py
+++ b/crm_request/tests/__init__.py
@@ -8,4 +8,9 @@
 #
 ##############################################################################
 
-from . import test_crm_claim_categories, test_crm_claim_request, test_my_profile
+from . import (
+    test_crm_claim_categories,
+    test_crm_claim_request,
+    test_my_profile,
+    test_request_notifications,
+)
diff --git a/crm_request/tests/test_request_notifications.py b/crm_request/tests/test_request_notifications.py
new file mode 100644
index 000000000..70458f1cc
--- /dev/null
+++ b/crm_request/tests/test_request_notifications.py
@@ -0,0 +1,93 @@
+##############################################################################
+#
+#    Copyright (C) 2026 Compassion CH (http://www.compassion.ch)
+#    Releasing children from poverty in Jesus' name
+#
+#    The licence is in the file __manifest__.py
+#
+##############################################################################
+from odoo.tests import TransactionCase, tagged
+
+EMAIL = """Return-Path: <form@example.com>
+From: Website form <form@example.com>
+Reply-To: volunteer-t3647@example.com
+To: {to}
+Subject: T3647 I want to help
+Message-ID: <t3647-{token}@example.com>
+Date: Wed, 04 Nov 2026 10:00:00 +0100
+Content-Type: text/plain; charset=utf-8
+
+I would like to know more about praying.
+"""
+
+
+@tagged("post_install", "-at_install")
+class TestRequestNotifications(TransactionCase):
+    """The responsible of a request created by e-mail gets one e-mail
+    (T3647)."""
+
+    @classmethod
+    def setUpClass(cls):
+        super().setUpClass()
+        cls.responsible = cls.env["res.users"].create(
+            {
+                "name": "T3647 responsible",
+                "login": "t3647-responsible",
+                "email": "t3647-responsible@example.com",
+                "notification_type": "email",
+                "groups_id": [(6, 0, cls.env.ref("base.group_user").ids)],
+            }
+        )
+        cls.alias = cls.env["mail.alias"].create(
+            {
+                "alias_name": "t3647-participate",
+                "alias_model_id": cls.env["ir.model"]._get_id("crm.claim"),
+                "alias_defaults": f"{{'user_id': {cls.responsible.id}}}",
+                "alias_contact": "everyone",
+            }
+        )
+
+    def receive(self, token):
+        thread_id = self.env["mail.thread"].message_process(
+            "crm.claim",
+            EMAIL.format(token=token, to=self.alias.alias_full_name or "t3647"),
+        )
+        return self.env["crm.claim"].browse(thread_id)
+
+    def notifications(self, request):
+        return self.env["mail.notification"].search(
+            [
+                ("mail_message_id.model", "=", "crm.claim"),
+                ("mail_message_id.res_id", "=", request.id),
+                ("res_partner_id", "=", self.responsible.partner_id.id),
+            ]
+        )
+
+    def test_one_email_for_the_responsible(self):
+        request = self.receive("one")
+
+        self.assertEqual(request.user_id, self.responsible)
+        self.assertIn(self.responsible.partner_id, request.message_partner_ids)
+        notifications = self.notifications(request)
+        self.assertEqual(
+            notifications.mail_message_id.mapped("message_type"),
+            ["email"],
+            "The responsible should only get the incoming e-mail, not the "
+            "'You have been assigned' e-mail as well",
+        )
+
+    def test_assigning_by_hand_still_notifies(self):
+        request = self.receive("by-hand")
+        other = self.responsible.copy({"login": "t3647-other"})
+
+        request.user_id = other
+
+        assigned = self.env["mail.message"].search(
+            [
+                ("model", "=", "crm.claim"),
+                ("res_id", "=", request.id),
+                ("message_type", "=", "user_notification"),
+                ("partner_ids", "in", other.partner_id.ids),
+            ]
+        )
+        self.assertTrue(assigned)