diff --git a/README.rst b/README.rst
index 2a0e8c2d..ee292438 100644
--- a/README.rst
+++ b/README.rst
@@ -58,7 +58,7 @@ describes an email, using the following schema:
     "from": "email",
     "subject": "string",
     "body": "html",
-    "attachments": [{"filename": "string", "content": "base64", "id": "string"}]
+    "attachments": [{"filename": "string", "content": "base64", "cid": "string"}]
   }
 
 -----------------
diff --git a/opwen_email_server/utils/email_parser.py b/opwen_email_server/utils/email_parser.py
index dc66f21d..79d9477b 100644
--- a/opwen_email_server/utils/email_parser.py
+++ b/opwen_email_server/utils/email_parser.py
@@ -45,7 +45,7 @@ def _parse_attachments(mailparts: Iterable[MailPart]) -> Iterable[dict]:
         if filename and payload:
             attachment = {'filename': filename, 'content': payload}
             if attachment_id:
-                attachment['id'] = attachment_id
+                attachment['cid'] = attachment_id
             yield attachment
 
 
diff --git a/tests/opwen_email_server/utils/test_email_parser.py b/tests/opwen_email_server/utils/test_email_parser.py
index f5171040..c3b283ff 100644
--- a/tests/opwen_email_server/utils/test_email_parser.py
+++ b/tests/opwen_email_server/utils/test_email_parser.py
@@ -75,9 +75,9 @@ def test_cid(self):
         attachments = email.get('attachments', [])
 
         self.assertEqual(len(attachments), 2)
-        self.assertIsNotNone(attachments[0].get('id'))
-        self.assertIsNotNone(attachments[1].get('id'))
-        self.assertNotEqual(attachments[0]['id'], attachments[1]['id'])
+        self.assertIsNotNone(attachments[0].get('cid'))
+        self.assertIsNotNone(attachments[1].get('cid'))
+        self.assertNotEqual(attachments[0]['cid'], attachments[1]['cid'])
 
     @classmethod
     def _given_mime_email(cls, filename, directory=TEST_DATA_DIRECTORY):