✨(attachments) configurable size limits with locale-aware formatting

src/backend/core/api/viewsets/inbound/mta.py

@@ -139,6 +139,21 @@ def deliver(self, request):
                 status=status.HTTP_400_BAD_REQUEST,
             )
 
+        # Validate incoming email size against configured limit
+        if len(raw_data) > settings.MAX_INCOMING_EMAIL_SIZE:
+            logger.error(
+                "Incoming email exceeds size limit: %d bytes (limit: %d bytes)",
+                len(raw_data),
+                settings.MAX_INCOMING_EMAIL_SIZE,
+            )
+            return Response(
+                {
+                    "status": "error",
+                    "detail": f"Email size exceeds maximum allowed size of {settings.MAX_INCOMING_EMAIL_SIZE} bytes",
+                },
+                status=status.HTTP_413_REQUEST_ENTITY_TOO_LARGE,
+            )
+
         logger.info(
             "Raw email received: %d bytes for %s",
             len(raw_data),

src/backend/core/api/viewsets/send.py

@@ -106,18 +106,14 @@ def post(self, request):
 
         self.check_object_permissions(request, message)
 
-        prepared = prepare_outbound_message(
+        # Prepare the message (raises ValidationError if size limits exceeded)
+        prepare_outbound_message(
             mailbox_sender,
             message,
             request.data.get("textBody"),
             request.data.get("htmlBody"),
             request.user,
         )
-        if not prepared:
-            raise drf_exceptions.APIException(
-                "Failed to prepare message for sending.",
-                code=status.HTTP_500_INTERNAL_SERVER_ERROR,
-            )
 
         # Launch async task for sending the message
         task = send_message_task.delay(str(message.id), must_archive=must_archive)

src/backend/core/mda/draft.py

@@ -4,7 +4,9 @@
 import uuid
 from typing import Optional
 
+from django.conf import settings
 from django.utils import timezone
+from django.utils.translation import gettext_lazy as _
 
 import rest_framework as drf
 
@@ -48,7 +50,7 @@ def create_draft(
 
     # Get or create sender contact
     mailbox_email = f"{mailbox.local_part}@{mailbox.domain.name}"
-    sender_contact, _ = models.Contact.objects.get_or_create(
+    sender_contact, _created = models.Contact.objects.get_or_create(
         email=mailbox_email,
         mailbox=mailbox,
         defaults={
@@ -195,7 +197,7 @@ def update_draft(
             # Create new recipients
             emails = update_data.get(recipient_type) or []
             for email in emails:
-                contact, _ = models.Contact.objects.get_or_create(
+                contact, _created = models.Contact.objects.get_or_create(
                     email=email,
                     mailbox=mailbox,
                     defaults={
@@ -292,6 +294,38 @@ def update_draft(
             to_add = new_attachments - current_attachment_ids
             to_remove = current_attachment_ids - new_attachments
 
+            # Validate total attachment size before adding
+            if to_add:
+                # Calculate current total (excluding attachments about to be removed)
+                current_attachments = message.attachments.exclude(id__in=to_remove)
+                current_total_size = sum(
+                    att.blob.size for att in current_attachments.select_related("blob")
+                )
+
+                # Calculate size of new attachments being added
+                new_attachments_objs = models.Attachment.objects.filter(
+                    id__in=to_add
+                ).select_related("blob")
+                new_total_size = sum(att.blob.size for att in new_attachments_objs)
+
+                # Check if adding these would exceed the limit
+                total_size = current_total_size + new_total_size
+                if total_size > settings.MAX_OUTGOING_EMAIL_SIZE:
+                    raise drf.exceptions.ValidationError(
+                        {
+                            "attachments": _(
+                                "Total attachment size (%(total_size)s bytes) exceeds maximum "
+                                "allowed size of %(max_size)s bytes. Current attachments: "
+                                "%(current_size)s bytes."
+                            )
+                            % {
+                                "total_size": total_size,
+                                "max_size": settings.MAX_OUTGOING_EMAIL_SIZE,
+                                "current_size": current_total_size,
+                            }
+                        }
+                    )
+
             # Remove attachments no longer in the list
             if to_remove:
                 message.attachments.remove(*to_remove)

src/backend/core/mda/outbound.py

@@ -7,6 +7,9 @@
 from django.conf import settings
 from django.core.cache import cache
 from django.utils import timezone
+from django.utils.translation import gettext_lazy as _
+
+import rest_framework as drf
 
 from core import models
 from core.enums import MessageDeliveryStatusChoices
@@ -150,9 +153,12 @@ def prepare_outbound_message(
     # Add attachments if present
     if message.attachments.exists():
         attachments = []
+        total_attachment_size = 0
+
         for attachment in message.attachments.select_related("blob").all():
             # Get the blob data
             blob = attachment.blob
+            total_attachment_size += blob.size
 
             # Add the attachment to the MIME data
             attachments.append(
@@ -178,7 +184,9 @@ def prepare_outbound_message(
         )
     except Exception as e:
         logger.error("Failed to compose MIME for message %s: %s", message.id, e)
-        return False
+        raise drf.exceptions.APIException(
+            _("Failed to compose email message.")
+        ) from e
 
     # Sign the message with DKIM
     dkim_signature_header: Optional[bytes] = sign_message_dkim(
@@ -190,6 +198,28 @@ def prepare_outbound_message(
         # Prepend the signature header
         raw_mime_signed = dkim_signature_header + b"\r\n" + raw_mime
 
+    # Validate total outgoing email size against configured limit
+    total_message_size = len(raw_mime_signed)
+    if total_message_size > settings.MAX_OUTGOING_EMAIL_SIZE:
+        logger.error(
+            "Total message size for message %s exceeds limit: %d bytes (limit: %d bytes)",
+            message.id,
+            total_message_size,
+            settings.MAX_OUTGOING_EMAIL_SIZE,
+        )
+        raise drf.exceptions.ValidationError(
+            {
+                "message": _(
+                    "Total message size (%(total_size)s bytes) exceeds maximum "
+                    "allowed size of %(max_size)s bytes."
+                )
+                % {
+                    "total_size": total_message_size,
+                    "max_size": settings.MAX_OUTGOING_EMAIL_SIZE,
+                }
+            }
+        )
+
     # Create a blob to store the raw MIME content
     blob = mailbox_sender.create_blob(
         content=raw_mime_signed,