diff --git a/src/postorius/forms.py b/src/postorius/forms.py
index 0328936..04d8b40 100644
--- a/src/postorius/forms.py
+++ b/src/postorius/forms.py
@@ -835,13 +835,6 @@
                 _('This email is in use. Please choose another or contact'
                   ' the administrator'), 'error')
 
-        # Check if the email is attached to a user in Mailman
-        try:
-            utils.get_client().get_user(email)
-            raise forms.ValidationError(
-                _('This email already belongs to a user'), 'error')
-        except HTTPError:
-            pass
         return email
 
 
diff --git a/src/postorius/tests/fixtures/vcr_cassettes/TestAddressActivationLinkSuccess.test_existing_user.yaml b/src/postorius/tests/fixtures/vcr_cassettes/TestAddressActivationLinkSuccess.test_existing_user.yaml
new file mode 100644
index 0000000..9770489
--- /dev/null
+++ b/src/postorius/tests/fixtures/vcr_cassettes/TestAddressActivationLinkSuccess.test_existing_user.yaml
@@ -0,0 +1,259 @@
+interactions:
+- request:
+    body: email=ler%40example.org&password=None
+    headers:
+      accept-encoding: ['gzip, deflate']
+      !!python/unicode content-type: [!!python/unicode application/x-www-form-urlencoded]
+    method: !!python/unicode POST
+    uri: http://localhost:9001/3.0/users
+  response:
+    body: {string: !!python/unicode ''}
+    headers:
+      content-length: ['0']
+      location: ['http://localhost:9001/3.0/users/36']
+    status: {code: 201, message: Created}
+- request:
+    body: email=les%40example.org&password=None
+    headers:
+      accept-encoding: ['gzip, deflate']
+      !!python/unicode content-type: [!!python/unicode application/x-www-form-urlencoded]
+    method: !!python/unicode POST
+    uri: http://localhost:9001/3.0/users
+  response:
+    body: {string: !!python/unicode ''}
+    headers:
+      content-length: ['0']
+      location: ['http://localhost:9001/3.0/users/37']
+    status: {code: 201, message: Created}
+- request:
+    body: null
+    headers:
+      accept-encoding: ['gzip, deflate']
+    method: !!python/unicode GET
+    uri: http://localhost:9001/3.0/users/ler@example.org
+  response:
+    body: {string: !!python/unicode '{"created_on": "2005-08-01T07:49:23", "http_etag":
+        "\"80be5db66e58bc06266ab6933e273d69ed62a895\"", "is_server_owner": false,
+        "password": "$6$rounds=712780$M0l.sgxEzkzCeDYD$2LFDRYejEvpjysYXJG6dq5eycN1GUr1lf/pWTiV/jGP77Nc3l2YJQXF40VSUwZf1Nti/o3sianZSyq4rIYSbd/",
+        "self_link": "http://localhost:9001/3.0/users/36", "user_id": 36}'}
+    headers:
+      content-length: ['326']
+      content-type: [application/json; charset=utf-8]
+    status: {code: 200, message: OK}
+- request:
+    body: null
+    headers:
+      accept-encoding: ['gzip, deflate']
+    method: !!python/unicode GET
+    uri: http://localhost:9001/3.0/users/36/addresses
+  response:
+    body: {string: !!python/unicode '{"entries": [{"email": "ler@example.org", "http_etag":
+        "\"200edc8cd699f99ec37a93e5ee6001d7a94a934c\"", "original_email": "ler@example.org",
+        "registered_on": "2005-08-01T07:49:23", "self_link": "http://localhost:9001/3.0/addresses/ler@example.org",
+        "user": "http://localhost:9001/3.0/users/36"}], "http_etag": "\"d4e56c1333a0709562bb8597b88e71706e5a196d\"",
+        "start": 0, "total_size": 1}'}
+    headers:
+      content-length: ['385']
+      content-type: [application/json; charset=utf-8]
+    status: {code: 200, message: OK}
+- request:
+    body: null
+    headers:
+      accept-encoding: ['gzip, deflate']
+    method: !!python/unicode GET
+    uri: http://localhost:9001/3.0/users/ler@example.org
+  response:
+    body: {string: !!python/unicode '{"created_on": "2005-08-01T07:49:23", "http_etag":
+        "\"80be5db66e58bc06266ab6933e273d69ed62a895\"", "is_server_owner": false,
+        "password": "$6$rounds=712780$M0l.sgxEzkzCeDYD$2LFDRYejEvpjysYXJG6dq5eycN1GUr1lf/pWTiV/jGP77Nc3l2YJQXF40VSUwZf1Nti/o3sianZSyq4rIYSbd/",
+        "self_link": "http://localhost:9001/3.0/users/36", "user_id": 36}'}
+    headers:
+      content-length: ['326']
+      content-type: [application/json; charset=utf-8]
+    status: {code: 200, message: OK}
+- request:
+    body: email=les%40example.org&absorb_existing=1
+    headers:
+      accept-encoding: ['gzip, deflate']
+      !!python/unicode content-type: [!!python/unicode application/x-www-form-urlencoded]
+    method: !!python/unicode POST
+    uri: http://localhost:9001/3.0/users/36/addresses
+  response:
+    body: {string: !!python/unicode ''}
+    headers:
+      content-length: ['0']
+      location: ['http://localhost:9001/3.0/addresses/les@example.org']
+    status: {code: 201, message: Created}
+- request:
+    body: null
+    headers:
+      accept-encoding: ['gzip, deflate']
+    method: !!python/unicode POST
+    uri: http://localhost:9001/3.0/addresses/les@example.org/verify
+  response:
+    body: {string: !!python/unicode ''}
+    headers:
+      content-length: ['0']
+    status: {code: 204, message: No Content}
+- request:
+    body: null
+    headers:
+      accept-encoding: ['gzip, deflate']
+    method: !!python/unicode GET
+    uri: http://localhost:9001/3.0/users/ler@example.org
+  response:
+    body: {string: !!python/unicode '{"created_on": "2005-08-01T07:49:23", "http_etag":
+        "\"80be5db66e58bc06266ab6933e273d69ed62a895\"", "is_server_owner": false,
+        "password": "$6$rounds=712780$M0l.sgxEzkzCeDYD$2LFDRYejEvpjysYXJG6dq5eycN1GUr1lf/pWTiV/jGP77Nc3l2YJQXF40VSUwZf1Nti/o3sianZSyq4rIYSbd/",
+        "self_link": "http://localhost:9001/3.0/users/36", "user_id": 36}'}
+    headers:
+      content-length: ['326']
+      content-type: [application/json; charset=utf-8]
+    status: {code: 200, message: OK}
+- request:
+    body: null
+    headers:
+      accept-encoding: ['gzip, deflate']
+    method: !!python/unicode GET
+    uri: http://localhost:9001/3.0/users/36/addresses
+  response:
+    body: {string: !!python/unicode '{"entries": [{"email": "ler@example.org", "http_etag":
+        "\"200edc8cd699f99ec37a93e5ee6001d7a94a934c\"", "original_email": "ler@example.org",
+        "registered_on": "2005-08-01T07:49:23", "self_link": "http://localhost:9001/3.0/addresses/ler@example.org",
+        "user": "http://localhost:9001/3.0/users/36"}, {"email": "les@example.org",
+        "http_etag": "\"fb740ff55957047e74c6156941ec9837f60581d1\"", "original_email":
+        "les@example.org", "registered_on": "2005-08-01T07:49:23", "self_link": "http://localhost:9001/3.0/addresses/les@example.org",
+        "user": "http://localhost:9001/3.0/users/36", "verified_on": "2005-08-01T07:49:23"}],
+        "http_etag": "\"d8edcc475fdd38e064eaaa0d8aa9a461ccafca36\"", "start": 0, "total_size":
+        2}'}
+    headers:
+      content-length: ['705']
+      content-type: [application/json; charset=utf-8]
+    status: {code: 200, message: OK}
+- request:
+    body: null
+    headers:
+      accept-encoding: ['gzip, deflate']
+    method: !!python/unicode GET
+    uri: http://localhost:9001/3.0/users/ler@example.org
+  response:
+    body: {string: !!python/unicode '{"created_on": "2005-08-01T07:49:23", "http_etag":
+        "\"80be5db66e58bc06266ab6933e273d69ed62a895\"", "is_server_owner": false,
+        "password": "$6$rounds=712780$M0l.sgxEzkzCeDYD$2LFDRYejEvpjysYXJG6dq5eycN1GUr1lf/pWTiV/jGP77Nc3l2YJQXF40VSUwZf1Nti/o3sianZSyq4rIYSbd/",
+        "self_link": "http://localhost:9001/3.0/users/36", "user_id": 36}'}
+    headers:
+      content-length: ['326']
+      content-type: [application/json; charset=utf-8]
+    status: {code: 200, message: OK}
+- request:
+    body: null
+    headers:
+      accept-encoding: ['gzip, deflate']
+    method: !!python/unicode GET
+    uri: http://localhost:9001/3.0/users/36/addresses
+  response:
+    body: {string: !!python/unicode '{"entries": [{"email": "ler@example.org", "http_etag":
+        "\"200edc8cd699f99ec37a93e5ee6001d7a94a934c\"", "original_email": "ler@example.org",
+        "registered_on": "2005-08-01T07:49:23", "self_link": "http://localhost:9001/3.0/addresses/ler@example.org",
+        "user": "http://localhost:9001/3.0/users/36"}, {"email": "les@example.org",
+        "http_etag": "\"fb740ff55957047e74c6156941ec9837f60581d1\"", "original_email":
+        "les@example.org", "registered_on": "2005-08-01T07:49:23", "self_link": "http://localhost:9001/3.0/addresses/les@example.org",
+        "user": "http://localhost:9001/3.0/users/36", "verified_on": "2005-08-01T07:49:23"}],
+        "http_etag": "\"d8edcc475fdd38e064eaaa0d8aa9a461ccafca36\"", "start": 0, "total_size":
+        2}'}
+    headers:
+      content-length: ['705']
+      content-type: [application/json; charset=utf-8]
+    status: {code: 200, message: OK}
+- request:
+    body: null
+    headers:
+      accept-encoding: ['gzip, deflate']
+    method: !!python/unicode GET
+    uri: http://localhost:9001/3.0/users/ler@example.org
+  response:
+    body: {string: !!python/unicode '{"created_on": "2005-08-01T07:49:23", "http_etag":
+        "\"80be5db66e58bc06266ab6933e273d69ed62a895\"", "is_server_owner": false,
+        "password": "$6$rounds=712780$M0l.sgxEzkzCeDYD$2LFDRYejEvpjysYXJG6dq5eycN1GUr1lf/pWTiV/jGP77Nc3l2YJQXF40VSUwZf1Nti/o3sianZSyq4rIYSbd/",
+        "self_link": "http://localhost:9001/3.0/users/36", "user_id": 36}'}
+    headers:
+      content-length: ['326']
+      content-type: [application/json; charset=utf-8]
+    status: {code: 200, message: OK}
+- request:
+    body: null
+    headers:
+      accept-encoding: ['gzip, deflate']
+    method: !!python/unicode GET
+    uri: http://localhost:9001/3.0/users/36
+  response:
+    body: {string: !!python/unicode '{"created_on": "2005-08-01T07:49:23", "http_etag":
+        "\"80be5db66e58bc06266ab6933e273d69ed62a895\"", "is_server_owner": false,
+        "password": "$6$rounds=712780$M0l.sgxEzkzCeDYD$2LFDRYejEvpjysYXJG6dq5eycN1GUr1lf/pWTiV/jGP77Nc3l2YJQXF40VSUwZf1Nti/o3sianZSyq4rIYSbd/",
+        "self_link": "http://localhost:9001/3.0/users/36", "user_id": 36}'}
+    headers:
+      content-length: ['326']
+      content-type: [application/json; charset=utf-8]
+    status: {code: 200, message: OK}
+- request:
+    body: null
+    headers:
+      accept-encoding: ['gzip, deflate']
+    method: !!python/unicode GET
+    uri: http://localhost:9001/3.0/users/36/addresses
+  response:
+    body: {string: !!python/unicode '{"entries": [{"email": "ler@example.org", "http_etag":
+        "\"200edc8cd699f99ec37a93e5ee6001d7a94a934c\"", "original_email": "ler@example.org",
+        "registered_on": "2005-08-01T07:49:23", "self_link": "http://localhost:9001/3.0/addresses/ler@example.org",
+        "user": "http://localhost:9001/3.0/users/36"}, {"email": "les@example.org",
+        "http_etag": "\"fb740ff55957047e74c6156941ec9837f60581d1\"", "original_email":
+        "les@example.org", "registered_on": "2005-08-01T07:49:23", "self_link": "http://localhost:9001/3.0/addresses/les@example.org",
+        "user": "http://localhost:9001/3.0/users/36", "verified_on": "2005-08-01T07:49:23"}],
+        "http_etag": "\"d8edcc475fdd38e064eaaa0d8aa9a461ccafca36\"", "start": 0, "total_size":
+        2}'}
+    headers:
+      content-length: ['705']
+      content-type: [application/json; charset=utf-8]
+    status: {code: 200, message: OK}
+- request:
+    body: null
+    headers:
+      accept-encoding: ['gzip, deflate']
+    method: !!python/unicode GET
+    uri: http://localhost:9001/3.0/domains
+  response:
+    body: {string: !!python/unicode '{"http_etag": "\"32223434a0f3af4cdc4673d1fbc5bac1f6d98fd3\"",
+        "start": 0, "total_size": 0}'}
+    headers:
+      content-length: ['90']
+      content-type: [application/json; charset=UTF-8]
+    status: {code: 200, message: OK}
+- request:
+    body: null
+    headers:
+      accept-encoding: ['gzip, deflate']
+    method: !!python/unicode GET
+    uri: http://localhost:9001/3.0/users
+  response:
+    body: {string: !!python/unicode '{"entries": [{"created_on": "2005-08-01T07:49:23",
+        "http_etag": "\"1c5db752cf25d65b8c5628f240cfc2a77ba33ded\"", "is_server_owner":
+        false, "password": "$6$rounds=698089$Gt7kUt0Gsn4ZEduV$DQBhVSJMs/yN9VMYJ6GVja11SxdW8bYDya91Xf5C9Le7ejStwuJIdc2.kYsyrJQG09OGw2fnizsKfnEs.9udA1",
+        "self_link": "http://localhost:9001/3.0/users/36", "user_id": 36}], "http_etag":
+        "\"a9de2de6a6c0e925565f35e4e5458cd60cdc9826\"", "start": 0, "total_size":
+        1}'}
+    headers:
+      content-length: ['429']
+      content-type: [application/json; charset=UTF-8]
+    status: {code: 200, message: OK}
+- request:
+    body: null
+    headers:
+      accept-encoding: ['gzip, deflate']
+    method: !!python/unicode DELETE
+    uri: http://localhost:9001/3.0/users/36
+  response:
+    body: {string: !!python/unicode ''}
+    headers:
+      content-length: ['0']
+    status: {code: 204, message: No Content}
+version: 1
diff --git a/src/postorius/tests/mailman_api_tests/test_address_activation.py b/src/postorius/tests/mailman_api_tests/test_address_activation.py
index 90c620a..8bd277a 100644
--- a/src/postorius/tests/mailman_api_tests/test_address_activation.py
+++ b/src/postorius/tests/mailman_api_tests/test_address_activation.py
@@ -64,10 +64,6 @@
         form = AddressActivationForm({'email': 'expired@example.org'})
         self.assertTrue(form.is_valid())
 
-    def test_email_used_by_mailman_is_invalid(self):
-        form = AddressActivationForm({'email': 'subscribed@example.org'})
-        self.assertFalse(form.is_valid())
-
 
 class TestAddressConfirmationProfile(ViewTestCase):
     """
@@ -173,3 +169,18 @@
             set(['ler@example.org', 'les@example.org']))
         logged_in_user = response.wsgi_request.user
         self.assertEqual(logged_in_user.other_emails, ['les@example.org'])
+
+    def test_existing_user(self):
+        # Add an existing address that is already linked to a user
+        self.mm_client.create_user("les@example.org", None)
+        self.client.login(username='ler', password='pwd')
+        url = reverse('address_activation_link',
+                      args=[self.profile.activation_key])
+        response = self.client.get(url)
+        self.assertRedirects(response, reverse('user_profile'))
+        self.assertHasSuccessMessage(response)
+        self.assertEqual(
+            set([a.email for a in self.mm_user.addresses]),
+            set(['ler@example.org', 'les@example.org']))
+        logged_in_user = response.wsgi_request.user
+        self.assertEqual(logged_in_user.other_emails, ['les@example.org'])
diff --git a/src/postorius/views/user.py b/src/postorius/views/user.py
index 887bcf8..bafd778 100644
--- a/src/postorius/views/user.py
+++ b/src/postorius/views/user.py
@@ -320,9 +320,13 @@
                 except Mailman404Error:
                     mailman_user = MailmanUser.objects.create(
                         request.user.email, '')
-                mm_address = mailman_user.add_address(profile.email)
+                # If the adress already exists, it's an import artefact: it's been
+                # validated by email, so it's safe to merge.
+                mm_address = mailman_user.add_address(
+                    profile.email, absorb_existing=True)
                 # The address has just been verified.
-                mm_address.verify()
+                if not mm_address.verified_on:
+                    mm_address.verify()
             except (MailmanApiError, MailmanConnectionError):
                 messages.error(request, _('The address could not be added.'))
                 return