fix: inbound attachment types

resend/__init__.py

@@ -31,8 +31,9 @@
 from .emails._batch import Batch, BatchValidationError
 from .emails._email import Email
 from .emails._emails import Emails, EmailTemplate
-from .emails._received_email import (EmailAttachment, EmailAttachmentDetails,
-                                     ListReceivedEmail, ReceivedEmail)
+from .emails._received_email import (AttachmentWithSignedUrl, EmailAttachment,
+                                     EmailAttachmentDetails, ListReceivedEmail,
+                                     ReceivedEmail)
 from .emails._receiving import Receiving as EmailsReceiving
 from .emails._tag import Tag
 from .events._event import (Event, EventListItem, EventSchema,
@@ -136,6 +137,7 @@
     "BatchValidationError",
     "ReceivedEmail",
     "EmailAttachment",
+    "AttachmentWithSignedUrl",
     "EmailAttachmentDetails",
     "ListReceivedEmail",
     # Receiving types (for type hints)

resend/emails/_attachments.py

@@ -4,7 +4,7 @@
 
 from resend import request
 from resend._base_response import BaseResponse
-from resend.emails._received_email import (EmailAttachment,
+from resend.emails._received_email import (AttachmentWithSignedUrl,
                                            EmailAttachmentDetails)
 from resend.pagination_helper import PaginationHelper
 
@@ -35,7 +35,7 @@ class _ListResponse(BaseResponse):
     """
     The object type: "list"
     """
-    data: List[EmailAttachment]
+    data: List[AttachmentWithSignedUrl]
     """
     The list of attachment objects.
     """
@@ -66,7 +66,7 @@ class ListResponse(_ListResponse):
 
         Attributes:
             object (str): The object type: "list"
-            data (List[EmailAttachment]): The list of attachment objects.
+            data (List[AttachmentWithSignedUrl]): The list of attachment objects.
             has_more (bool): Whether there are more attachments available for pagination.
         """
 

resend/emails/_received_email.py

@@ -1,21 +1,26 @@
 from typing import Dict, List, Optional
 
-from typing_extensions import NotRequired, TypedDict
+from typing_extensions import Literal, NotRequired, TypedDict
 
 from resend._base_response import BaseResponse
 
 
 class EmailAttachment(TypedDict):
     """
-    EmailAttachment type that wraps an attachment object from an email.
+    Attachment metadata embedded in a received (inbound) email, as returned by
+    ``Emails.Receiving.get`` and ``Emails.Receiving.list``.
+
+    These are raw values from the inbound MIME parts, so ``filename``,
+    ``content_id``, and ``content_disposition`` can be null (e.g. S/MIME
+    signatures or calendar invites), and ``size`` is null in list responses.
 
     Attributes:
         id (str): The attachment ID.
         filename (Optional[str]): The filename of the attachment.
         content_type (str): The content type of the attachment.
+        content_id (Optional[str]): The content ID for inline attachments.
         content_disposition (Optional[str]): The content disposition of the attachment.
-        content_id (NotRequired[str]): The content ID for inline attachments.
-        size (NotRequired[int]): The size of the attachment in bytes.
+        size (Optional[int]): The size of the attachment in bytes.
     """
 
     id: str
@@ -30,58 +35,59 @@ class EmailAttachment(TypedDict):
     """
     The content type of the attachment.
     """
-    content_disposition: Optional[str]
+    content_id: Optional[str]
     """
-    The content disposition of the attachment.
+    The content ID for inline attachments.
     """
-    content_id: NotRequired[str]
+    content_disposition: Optional[str]
     """
-    The content ID for inline attachments.
+    The content disposition of the attachment.
     """
-    size: NotRequired[int]
+    size: Optional[int]
     """
     The size of the attachment in bytes.
     """
 
 
-class EmailAttachmentDetails(TypedDict):
+class AttachmentWithSignedUrl(TypedDict):
     """
-    EmailAttachmentDetails type that wraps an email attachment with download details.
+    Attachment returned by the signed-URL endpoints that list or retrieve
+    attachments (for both sent and received emails).
 
     Attributes:
-        object (str): The object type.
         id (str): The attachment ID.
-        filename (Optional[str]): The filename of the attachment.
+        filename (NotRequired[str]): The filename of the attachment.
         content_type (str): The content type of the attachment.
-        content_disposition (Optional[str]): The content disposition of the attachment.
         content_id (NotRequired[str]): The content ID for inline attachments.
+        content_disposition (Literal["inline", "attachment"]): The content disposition of the attachment.
+        size (int): The size of the attachment in bytes.
         download_url (str): The URL to download the attachment.
         expires_at (str): When the download URL expires.
     """
 
-    object: str
-    """
-    The object type.
-    """
     id: str
     """
     The attachment ID.
     """
-    filename: Optional[str]
+    filename: NotRequired[str]
     """
     The filename of the attachment.
     """
     content_type: str
     """
     The content type of the attachment.
     """
-    content_disposition: Optional[str]
+    content_id: NotRequired[str]
+    """
+    The content ID for inline attachments.
+    """
+    content_disposition: Literal["inline", "attachment"]
     """
     The content disposition of the attachment.
     """
-    content_id: NotRequired[str]
+    size: int
     """
-    The content ID for inline attachments.
+    The size of the attachment in bytes.
     """
     download_url: str
     """
@@ -93,6 +99,29 @@ class EmailAttachmentDetails(TypedDict):
     """
 
 
+class EmailAttachmentDetails(AttachmentWithSignedUrl):
+    """
+    A single attachment retrieved from a dedicated attachment endpoint. Same as
+    ``AttachmentWithSignedUrl`` with an added ``object`` field.
+
+    Attributes:
+        object (str): The object type.
+        id (str): The attachment ID.
+        filename (NotRequired[str]): The filename of the attachment.
+        content_type (str): The content type of the attachment.
+        content_id (NotRequired[str]): The content ID for inline attachments.
+        content_disposition (Literal["inline", "attachment"]): The content disposition of the attachment.
+        size (int): The size of the attachment in bytes.
+        download_url (str): The URL to download the attachment.
+        expires_at (str): When the download URL expires.
+    """
+
+    object: str
+    """
+    The object type.
+    """
+
+
 # Uses functional typed dict syntax here in order to support "from" reserved keyword
 _ReceivedEmailFromParam = TypedDict(
     "_ReceivedEmailFromParam",

resend/emails/_receiving.py

@@ -4,7 +4,7 @@
 
 from resend import request
 from resend._base_response import BaseResponse
-from resend.emails._received_email import (EmailAttachment,
+from resend.emails._received_email import (AttachmentWithSignedUrl,
                                            EmailAttachmentDetails,
                                            ListReceivedEmail, ReceivedEmail)
 from resend.pagination_helper import PaginationHelper
@@ -66,7 +66,7 @@ class _AttachmentListResponse(BaseResponse):
     """
     The object type: "list"
     """
-    data: List[EmailAttachment]
+    data: List[AttachmentWithSignedUrl]
     """
     The list of attachment objects.
     """
@@ -102,7 +102,7 @@ class ListResponse(_AttachmentListResponse):
 
             Attributes:
                 object (str): The object type: "list"
-                data (List[EmailAttachment]): The list of attachment objects.
+                data (List[AttachmentWithSignedUrl]): The list of attachment objects.
                 has_more (bool): Whether there are more attachments available for pagination.
             """
 

tests/attachments_async_test.py

@@ -56,6 +56,8 @@ async def test_sent_email_attachments_list_async(self) -> None:
                         "content_type": "image/png",
                         "content_disposition": "inline",
                         "size": 1024,
+                        "download_url": "https://cdn.resend.com/emails/test/attachments/test-id",
+                        "expires_at": "2025-10-17T14:29:41.521Z",
                     }
                 ],
             }

tests/attachments_test.py

@@ -86,13 +86,17 @@
                         "content_disposition": "inline",
                         "content_id": "img001",
                         "size": 1024,
+                        "download_url": "https://inbound-cdn.resend.com/test/attachments/2a0c9ce0?signature=sig-123",
+                        "expires_at": "2025-10-17T14:29:41.521Z",
                     },
                     {
                         "id": "3b1d0df1-4223-5839-a87f-58eecd27b429",
                         "filename": "document.pdf",
                         "content_type": "application/pdf",
                         "content_disposition": "attachment",
                         "size": 2048,
+                        "download_url": "https://inbound-cdn.resend.com/test/attachments/3b1d0df1?signature=sig-456",
+                        "expires_at": "2025-10-17T14:29:41.521Z",
                     },
                 ],
             }
@@ -110,6 +114,8 @@
         assert attachments["data"][0]["id"] == "2a0c9ce0-3112-4728-976e-47ddcd16a318"
         assert attachments["data"][0]["filename"] == "avatar.png"
         assert attachments["data"][0]["size"] == 1024
+        assert "https://inbound-cdn.resend.com" in attachments["data"][0]["download_url"]
+        assert attachments["data"][0]["expires_at"] == "2025-10-17T14:29:41.521Z"
         assert attachments["data"][1]["id"] == "3b1d0df1-4223-5839-a87f-58eecd27b429"
         assert attachments["data"][1]["filename"] == "document.pdf"
 
@@ -125,6 +131,8 @@
                         "content_type": "image/png",
                         "content_disposition": "inline",
                         "size": 1024,
+                        "download_url": "https://inbound-cdn.resend.com/test/attachments/2a0c9ce0?signature=sig-123",
+                        "expires_at": "2025-10-17T14:29:41.521Z",
                     },
                 ],
             }

tests/emails_test.py

@@ -280,6 +280,7 @@ def test_receiving_get(self) -> None:
                         "content_type": "application/pdf",
                         "content_id": "cid_123",
                         "content_disposition": "attachment",
+                        "size": 4096,
                     }
                 ],
             }
@@ -332,6 +333,61 @@ def test_receiving_get_with_no_attachments(self) -> None:
         assert email["reply_to"] is None
         assert len(email["attachments"]) == 0
 
+    def test_receiving_get_with_nullable_attachment_fields(self) -> None:
+        # Inbound MIME parts (S/MIME signatures, calendar invites) can return
+        # null for filename, content_id, and content_disposition.
+        # See: https://linear.app/resend/issue/DEV-934
+        self.set_mock_json(
+            {
+                "object": "inbound",
+                "id": "67d9bcdb-5a02-42d7-8da9-0d6feea18cff",
+                "to": ["received@example.com"],
+                "from": "sender@example.com",
+                "created_at": "2023-04-07T23:13:52.669661+00:00",
+                "subject": "Signed inbound email",
+                "html": None,
+                "text": "hello world",
+                "bcc": None,
+                "cc": None,
+                "reply_to": None,
+                "headers": {},
+                "message_id": "<msg@example.com>",
+                "attachments": [
+                    {
+                        "id": "f5e32216-3017-4118-97d5-5c84d991bf98",
+                        "filename": "smime.p7s",
+                        "content_type": "application/pkcs7-signature",
+                        "content_id": None,
+                        "content_disposition": "attachment",
+                        "size": 1361,
+                    },
+                    {
+                        "id": "68136802-3577-4911-a7d2-b303e61261ac",
+                        "filename": None,
+                        "content_type": "text/calendar",
+                        "content_id": None,
+                        "content_disposition": None,
+                        "size": 1152,
+                    },
+                ],
+            }
+        )
+
+        email: resend.ReceivedEmail = resend.Emails.Receiving.get(
+            email_id="67d9bcdb-5a02-42d7-8da9-0d6feea18cff",
+        )
+        assert len(email["attachments"]) == 2
+
+        smime = email["attachments"][0]
+        assert smime["filename"] == "smime.p7s"
+        assert smime["content_disposition"] == "attachment"
+        assert smime["content_id"] is None
+
+        calendar = email["attachments"][1]
+        assert calendar["filename"] is None
+        assert calendar["content_disposition"] is None
+        assert calendar["content_id"] is None
+
     def test_should_receiving_get_raise_exception_when_no_content(self) -> None:
         self.set_mock_json(None)
         with self.assertRaises(NoContentError):

tests/receiving_async_test.py

@@ -117,13 +117,17 @@ async def test_receiving_attachments_list_async(self) -> None:
                         "content_disposition": "inline",
                         "content_id": "img001",
                         "size": 1024,
+                        "download_url": "https://inbound-cdn.resend.com/test/attachments/2a0c9ce0?signature=sig-123",
+                        "expires_at": "2025-10-17T14:29:41.521Z",
                     },
                     {
                         "id": "3b1d0df1-4223-5839-a87f-58eecd27b429",
                         "filename": "document.pdf",
                         "content_type": "application/pdf",
                         "content_disposition": "attachment",
                         "size": 2048,
+                        "download_url": "https://inbound-cdn.resend.com/test/attachments/3b1d0df1?signature=sig-456",
+                        "expires_at": "2025-10-17T14:29:41.521Z",
                     },
                 ],
             }

tests/response_test.py

@@ -18,6 +18,8 @@ def test_list_response_supports_dict_access(self) -> None:
                         "content_type": "image/png",
                         "content_disposition": "inline",
                         "size": 1024,
+                        "download_url": "https://cdn.resend.com/att-1",
+                        "expires_at": "2025-10-17T14:29:41.521Z",
                     },
                 ],
             }
@@ -28,6 +30,7 @@ def test_list_response_supports_dict_access(self) -> None:
         assert attachments["has_more"] is False
         assert len(attachments["data"]) == 1
         assert attachments["data"][0]["id"] == "att-1"
+        assert attachments["data"][0]["download_url"] == "https://cdn.resend.com/att-1"
 
     def test_list_response_supports_attribute_access(self) -> None:
         self.set_mock_json(
@@ -41,6 +44,8 @@ def test_list_response_supports_attribute_access(self) -> None:
                         "content_type": "image/png",
                         "content_disposition": "inline",
                         "size": 1024,
+                        "download_url": "https://cdn.resend.com/att-1",
+                        "expires_at": "2025-10-17T14:29:41.521Z",
                     },
                 ],
             }