diff --git a/opwen_email_server/actions.py b/opwen_email_server/actions.py
index e6e8d676..a7bffdd4 100644
--- a/opwen_email_server/actions.py
+++ b/opwen_email_server/actions.py
@@ -1,10 +1,13 @@
 from abc import ABC
+from hashlib import sha256
 from typing import Callable
 from typing import Iterable
 from typing import Tuple
 from typing import Union
 from uuid import uuid4
 
+from libcloud.storage.types import ObjectDoesNotExistError
+
 from opwen_email_server.constants import events
 from opwen_email_server.constants import sync
 from opwen_email_server.services.auth import AzureAuth
@@ -78,7 +81,11 @@ def __init__(self,
         self._email_parser = email_parser or self._parse_mime_email
 
     def _action(self, resource_id):  # type: ignore
-        mime_email = self._raw_email_storage.fetch_text(resource_id)
+        try:
+            mime_email = self._raw_email_storage.fetch_text(resource_id)
+        except ObjectDoesNotExistError:
+            self.log_warning('Inbound email %s does not exist', resource_id)
+            return 'skipped', 202
 
         email = self._email_parser(mime_email)
         self._store_inbound_email(resource_id, email)
@@ -150,13 +157,11 @@ class ReceiveInboundEmail(_Action):
     def __init__(self,
                  auth: AzureAuth,
                  raw_email_storage: AzureTextStorage,
-                 next_task: Callable[[str], None],
-                 email_id_source: Callable[[], str] = None):
+                 next_task: Callable[[str], None]):
 
         self._auth = auth
         self._raw_email_storage = raw_email_storage
         self._next_task = next_task
-        self._email_id_source = email_id_source or self._new_email_id
 
     def _action(self, client_id, email):  # type: ignore
         domain = self._auth.domain_for(client_id)
@@ -164,7 +169,7 @@ def _action(self, client_id, email):  # type: ignore
             self.log_event(events.UNREGISTERED_CLIENT, {'client_id': client_id})  # noqa: E501
             return 'client is not registered', 403
 
-        email_id = self._email_id_source()
+        email_id = self._new_email_id(email)
 
         self._raw_email_storage.store_text(email_id, email)
 
@@ -174,8 +179,8 @@ def _action(self, client_id, email):  # type: ignore
         return 'received', 200
 
     @classmethod
-    def _new_email_id(cls) -> str:
-        return str(uuid4())
+    def _new_email_id(cls, email: str) -> str:
+        return sha256(email.encode('utf-8')).hexdigest()
 
 
 class DownloadClientEmails(_Action):
diff --git a/opwen_email_server/services/storage.py b/opwen_email_server/services/storage.py
index e086dc7f..1146e7d2 100644
--- a/opwen_email_server/services/storage.py
+++ b/opwen_email_server/services/storage.py
@@ -74,9 +74,13 @@ def ensure_exists(self):
         self._client
 
     def delete(self, resource_id: str):
-        resource = self._client.get_object(resource_id)
-        resource.delete()
-        self.log_debug('deleted %s', resource_id)
+        try:
+            resource = self._client.get_object(resource_id)
+        except ObjectDoesNotExistError:
+            self.log_warning('deleted missing %s', resource_id)
+        else:
+            resource.delete()
+            self.log_debug('deleted %s', resource_id)
 
     def iter(self) -> Iterator[str]:
         for resource in self._client.list_objects():
diff --git a/tests/files/end_to_end/client-emails.tar.gz b/tests/files/end_to_end/client-emails.tar.gz
index 95284f45..857e80d6 100644
Binary files a/tests/files/end_to_end/client-emails.tar.gz and b/tests/files/end_to_end/client-emails.tar.gz differ
diff --git a/tests/files/end_to_end/inbound-email.mime b/tests/files/end_to_end/inbound-email.mime
index 6ea68e25..906291dc 100644
--- a/tests/files/end_to_end/inbound-email.mime
+++ b/tests/files/end_to_end/inbound-email.mime
@@ -11,7 +11,7 @@ From: Clemens Wolff <clemens.wolff@gmail.com>
 Date: Sun, 12 Feb 2017 22:25:01 -0800
 Message-ID: <CAL79TcnjhV5PinZVY8Y3QEoNNcSa9uuNU5N3EP-gqcYPFfuHLA@mail.gmail.com>
 Subject: Test email sent to Lokole client
-To: clemens@developer.lokole.ca, laura@developer.lokole.ca
+To: clemens@developer1.lokole.ca, laura@developer1.lokole.ca, nzola@developer2.lokole.ca
 Content-Type: multipart/alternative; boundary=001a1146392641b94705486384bf
 
 --001a1146392641b94705486384bf
diff --git a/tests/integration/0-register-client.sh b/tests/integration/0-register-client.sh
index fc08fca1..f40f4794 100755
--- a/tests/integration/0-register-client.sh
+++ b/tests/integration/0-register-client.sh
@@ -9,9 +9,9 @@ mkdir -p "${out_dir}"
 curl -fs \
   -H "Content-Type: application/json" \
   -u "admin:password" \
-  -d '{"domain":"developer.lokole.ca"}' \
+  -d '{"domain":"developer1.lokole.ca"}' \
   "http://localhost:8080/api/email/register/" \
-| tee "${out_dir}/register.json"
+| tee "${out_dir}/register1.json"
 
 # registering a client with bad credentials should fail
 if curl -fs \
@@ -20,3 +20,11 @@ if curl -fs \
   -d '{"domain":"hacker.lokole.ca"}' \
   "http://localhost:8080/api/email/register/" \
 ; then echo "Was able to register a client with bad credentials" >&2; exit 4; fi
+
+# also register another client to simulate multi-client emails
+curl -fs \
+  -H "Content-Type: application/json" \
+  -u "admin:password" \
+  -d '{"domain":"developer2.lokole.ca"}' \
+  "http://localhost:8080/api/email/register/" \
+| tee "${out_dir}/register2.json"
diff --git a/tests/integration/1-client-uploads-emails.sh b/tests/integration/1-client-uploads-emails.sh
index bf6d3282..509ac774 100755
--- a/tests/integration/1-client-uploads-emails.sh
+++ b/tests/integration/1-client-uploads-emails.sh
@@ -6,8 +6,8 @@ out_dir="$(dirname "$0")/../files/end_to_end/test.out"
 mkdir -p "${out_dir}"
 
 emails_to_send="${in_dir}/client-emails.tar.gz"
-client_id="$(jq -r '.client_id' < "${out_dir}/register.json")"
-resource_container="$(jq -r '.resource_container' < "${out_dir}/register.json")"
+client_id="$(jq -r '.client_id' < "${out_dir}/register1.json")"
+resource_container="$(jq -r '.resource_container' < "${out_dir}/register1.json")"
 resource_id="$(python3 -c 'import uuid;print(str(uuid.uuid4()))').tar.gz"
 
 # workflow 1: send emails written on the client to the world
diff --git a/tests/integration/2-receive-email-for-client.sh b/tests/integration/2-receive-email-for-client.sh
index 5b973596..8bc56002 100755
--- a/tests/integration/2-receive-email-for-client.sh
+++ b/tests/integration/2-receive-email-for-client.sh
@@ -7,7 +7,7 @@ mkdir -p "${out_dir}"
 
 email_to_receive="${in_dir}/inbound-email.mime"
 
-client_id="$(jq -r '.client_id' < "${out_dir}/register.json")"
+client_id="$(jq -r '.client_id' < "${out_dir}/register1.json")"
 
 # workflow 2a: receive an email directed at one of the clients
 # this simulates sendgrid delivering an email to the service
@@ -15,3 +15,9 @@ curl -fs \
   -H "Content-Type: multipart/form-data" \
   -F "email=$(cat "${email_to_receive}")" \
   "http://localhost:8080/api/email/sendgrid/${client_id}"
+
+# simulate delivery of the same email to the second mailbox
+curl -fs \
+  -H "Content-Type: multipart/form-data" \
+  -F "email=$(cat "${email_to_receive}")" \
+  "http://localhost:8080/api/email/sendgrid/${client_id}"
diff --git a/tests/integration/3-client-downloads-emails.sh b/tests/integration/3-client-downloads-emails.sh
index 3b6ebf0f..4488aee2 100755
--- a/tests/integration/3-client-downloads-emails.sh
+++ b/tests/integration/3-client-downloads-emails.sh
@@ -4,8 +4,10 @@ set -euo pipefail
 out_dir="$(dirname "$0")/../files/end_to_end/test.out"
 mkdir -p "${out_dir}"
 
-client_id="$(jq -r '.client_id' < "${out_dir}/register.json")"
-resource_container="$(jq -r '.resource_container' < "${out_dir}/register.json")"
+for i in 1 2; do
+
+client_id="$(jq -r '.client_id' < "${out_dir}/register${i}.json")"
+resource_container="$(jq -r '.resource_container' < "${out_dir}/register${i}.json")"
 
 # workflow 2b: deliver emails written by the world to a lokole client
 # first the client makes a request to ask the server to package up all the
@@ -14,21 +16,25 @@ resource_container="$(jq -r '.resource_container' < "${out_dir}/register.json")"
 curl -fs \
   -H "Accept: application/json" \
   "http://localhost:8080/api/email/download/${client_id}" \
-| tee "${out_dir}/download.json"
+| tee "${out_dir}/download${i}.json"
 
-resource_id="$(jq -r '.resource_id' < "${out_dir}/download.json")"
+resource_id="$(jq -r '.resource_id' < "${out_dir}/download${i}.json")"
 
 # now we simulate the client downloading the package from the shared blob storage
 curl -fs \
   "http://localhost:10000/devstoreaccount1/${resource_container}/${resource_id}" \
-> "${out_dir}/downloaded.tar.gz"
+> "${out_dir}/downloaded${i}.tar.gz"
 
-tar xzf "${out_dir}/downloaded.tar.gz" -C "${out_dir}"
+tar xzf "${out_dir}/downloaded${i}.tar.gz" -C "${out_dir}"
 
 num_emails_actual="$(wc -l "${out_dir}/emails.jsonl" | cut -d' ' -f1)"
 num_emails_expected=1
 
 if [[ "${num_emails_actual}" -ne "${num_emails_expected}" ]]; then
-  echo "Got ${num_emails_actual} but expected ${num_emails_expected}" >&2
+  echo "Got ${num_emails_actual} emails but expected ${num_emails_expected}" >&2
   exit 1
 fi
+
+rm "${out_dir}/emails.jsonl"
+
+done
diff --git a/tests/integration/assert.sh b/tests/integration/assert.sh
index 9bea4e5e..9ffb8f27 100755
--- a/tests/integration/assert.sh
+++ b/tests/integration/assert.sh
@@ -4,14 +4,6 @@ set -euo pipefail
 out_dir="$(dirname "$0")/../files/end_to_end/test.out"
 mkdir -p "${out_dir}"
 
-num_emails_actual="$(wc -l "${out_dir}/emails.jsonl" | cut -d' ' -f1)"
-num_emails_expected=1
-
-if [[ "${num_emails_actual}" -ne "${num_emails_expected}" ]]; then
-  echo "Got ${num_emails_actual} emails but expected ${num_emails_expected}" >&2
-  exit 1
-fi
-
 sql_query() {
   docker-compose exec postgres psql -Aqt -c "$1" -U ascoderu -d telemetry \
   | tr -d -C '0-9'
diff --git a/tests/opwen_email_server/services/test_storage.py b/tests/opwen_email_server/services/test_storage.py
index a2218cdc..d0bd70a1 100644
--- a/tests/opwen_email_server/services/test_storage.py
+++ b/tests/opwen_email_server/services/test_storage.py
@@ -101,6 +101,8 @@ def test_stores_fetches_and_deletes_file(self):
         with self.assertRaises(ObjectDoesNotExistError):
             self._storage.fetch_file(resource_id)
 
+        self._storage.delete(resource_id)
+
     def assertFileContains(self, path: str, content: str):
         with open(path, encoding='utf-8') as fobj:
             self.assertEqual(fobj.read(), content)
diff --git a/tests/opwen_email_server/test_actions.py b/tests/opwen_email_server/test_actions.py
index fcb78989..6f9a8b02 100644
--- a/tests/opwen_email_server/test_actions.py
+++ b/tests/opwen_email_server/test_actions.py
@@ -6,6 +6,8 @@
 from unittest.mock import patch
 from uuid import uuid4
 
+from libcloud.storage.types import ObjectDoesNotExistError
+
 from opwen_email_server import actions
 from opwen_email_server.constants import sync
 from opwen_email_server.services.storage import AccessInfo
@@ -85,6 +87,25 @@ def setUp(self):
         self.pending_factory = MagicMock()
         self.email_parser = MagicMock()
 
+    def test_202(self):
+        # noinspection PyUnusedLocal
+        def throw(*args, **kwargs):
+            raise ObjectDoesNotExistError(None, None, None)
+
+        resource_id = str(uuid4())
+
+        self.raw_email_storage.fetch_text.side_effect = throw
+
+        _, status = self._execute_action(resource_id)
+
+        self.assertEqual(status, 202)
+        self.raw_email_storage.fetch_text.assert_called_once_with(resource_id)
+        self.assertFalse(self.raw_email_storage.delete.called)
+        self.assertFalse(self.email_storage.store_object.called)
+        self.assertFalse(self.pending_factory.called)
+        self.assertFalse(self.pending_storage.store_text.called)
+        self.assertFalse(self.email_parser.called)
+
     def test_200(self):
         resource_id = str(uuid4())
         domain = 'test.com'
@@ -175,27 +196,44 @@ def test_403(self):
 
     def test_200(self):
         client_id = str(uuid4())
-        email_id = str(uuid4())
+        email_id = 'dfbab492b9adcf20ca8424b993b0f7ec26731d069be4d451ebbf7910937a999c'
         domain = 'test.com'
         email = 'dummy-mime'
 
         self.auth.domain_for.return_value = domain
-        self.email_id_source.return_value = email_id
 
         _, status = self._execute_action(client_id, email)
 
         self.assertEqual(status, 200)
         self.auth.domain_for.assert_called_once_with(client_id)
-        self.email_id_source.assert_called_once_with()
         self.raw_email_storage.store_text.assert_called_once_with(email_id, email)
         self.next_task.assert_called_once_with(email_id)
 
+    def test_is_idempotent(self):
+        client_id = str(uuid4())
+        domain = 'test.com'
+        email = 'dummy-mime'
+        num_repeated_emails = 3
+
+        self.auth.domain_for.return_value = domain
+
+        for _ in range(num_repeated_emails):
+            _, status = self._execute_action(client_id, email)
+            self.assertEqual(status, 200)
+
+        self.assertHasSameCalls(self.raw_email_storage.store_text, num_repeated_emails)
+        self.assertHasSameCalls(self.next_task, num_repeated_emails)
+
+    def assertHasSameCalls(self, mocked_function, num_calls):
+        self.assertEqual(len(mocked_function.call_args_list), num_calls)
+        for call in mocked_function.call_args_list:
+            self.assertEqual(call, mocked_function.call_args_list[0])
+
     def _execute_action(self, *args, **kwargs):
         action = actions.ReceiveInboundEmail(
             auth=self.auth,
             raw_email_storage=self.raw_email_storage,
-            next_task=self.next_task,
-            email_id_source=self.email_id_source)
+            next_task=self.next_task)
 
         return action(*args, **kwargs)