Add Sweego email backend with inbound support#457
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- Add Sweego backend for transactional email via /send API - Add bulk sending support via /send/bulk/email endpoint - Add tracking webhook support with signature validation - Add inbound email webhook with lazy-loading attachments - Add comprehensive documentation with batch sending examples - Add 65 tests (34 backend + 31 webhooks) Sweego (https://www.sweego.io) is a French email service provider focused on transactional email and SMS. This implementation supports: * Single and batch sending with template variables * Automatic endpoint selection (/send vs /send/bulk/email) * Tracking webhooks (sent, delivered, bounced, opened, clicked, etc.) * Inbound email routing with lazy attachment loading * ESP stored templates * Metadata (via X-Metadata-* headers) * Tags (via campaign-tags) * All standard Anymail features The inbound implementation uses a unique lazy-loading approach for attachments, where attachment metadata is provided in the webhook but content is fetched on-demand via Sweego's API. Closes anymail#456
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@pydubreucq thanks for this, looks very thorough! I like the LazyAttachment idea. I'll do a closer review (and get set up for integration tests) sometime in the next week. A few suggestions from my initial look:
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Hi,
Thanks a lot for your first review.
Don't waste your time just yet, I'm going to correct your initial feedback
first.
Thanks again.
Best,
Pierre-Yves
Le ven. 16 janv. 2026 à 01:03, Mike Edmunds ***@***.***> a
écrit :
… *medmunds* left a comment (anymail/django-anymail#457)
<#457 (comment)>
@pydubreucq <https://github.com/pydubreucq> thanks for this, looks very
thorough! I like the LazyAttachment idea.
I'll do a closer review (and get set up for integration tests) sometime in
the next week. A few suggestions from my initial look:
- It might make sense to treat cc (and maybe bcc) as unsupported
features, rather than mapping them to to recipients. (In general, any
situation where data would be lost or interpreted in a way the caller
wouldn't expect should be treated as "unsupported".)
- Or, if Sweego allows "Cc" and "To" in the custom headers, the best
way to handle cc (and non-batch multiple-to recipients) is composing
display headers that match the sender's intent. And then treat the API
to field as a list of envelope recipients. (The Unisender Go and
Sparkpost backends both use variations on this.) In that case, using
payload.is_batch() is the best way to determine which API to use.
- For metadata, what we've done with some other ESPs is a single
X-Metadata header that is JSON serialized, rather than a separate
metadata header per key—particularly with the API limitation on the number
of custom headers. (Unless Sweego has special dashboard handling for
X-Metdata-<key> headers.)
- Please don't use f'"{name}" <{email}>' to construct email
addresses—it creates a header injection vulnerability. You can use
anymail.utils.EmailAddress to construct and safely serialize an address.
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- Add conditional cc/bcc support (/send only, not /send/bulk/email) - Fix endpoint selection: use /send/bulk/email only for 2+ recipients with merge_data - Remove X-Metadata- prefix from metadata headers - Add API endpoint comparison table to documentation - Update metadata documentation to explain x- prefix behavior - Use email.headerregistry.Address() to prevent header injection - Fix tests to match new behavior Relates to anymail#456
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@medmunds Thank you for the thorough review! I've addressed all your points:
All 67 tests passing. Ready for another review when you have time :) |
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@pydubreucq it would be helpful if you could have a human developer review this code. I'm going to mark it "draft" for now. Your AI has confused email headers with Anymail's metadata, in a way that breaks sending and also doesn't work with the metadata retrieval in the tracking webhook. I suspect there are other problems, but stopped looking after that. |
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Hello, |
medmunds
left a comment
medmunds
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@pydubreucq I've been struggling to figure out how to provide useful feedback on this PR.
Your AI has confused metadata, template substitution variables, and email (MIME) headers—repeatedly. The corrections from the human developer made it worse.
There are also repeated problems with silently re-interpreting the user's requests to fit Sweego's API. Anymail tries to be strict about either using the user's data as they intended or raising an error.
I've pointed out several specific issues I saw in the comments, but there are many more. Clearly nobody has tried to use this code to send messages and verify that what's actually sent matches what the code tries to send. (Suggestion: run the integration tests, substituting your own email addresses, then closely examine the resulting message headers and tracking webhook payloads.)
This is still very much an AI-generated PR that has not been carefully reviewed by a human developer familiar with Anymail. Even with fixes to the problems I identified here, it's not something I could consider merging without a lot more work.
| def set_metadata(self, metadata): | ||
| # Sweego exposes metadata through custom headers | ||
| # Limited to 5 custom headers total | ||
| if metadata: | ||
| self.data.setdefault("headers", {}).update( | ||
| {k: str(v) for k, v in list(metadata.items())[:5]} | ||
| ) |
There was a problem hiding this comment.
Metadata is not the same thing as email headers. Metadata is arbitrary key-value information associated with the message, meant to be available in tracking webhooks. (Humans can read about metadata in Anymail's docs. AIs should carefully review docs/sending/anymail_additions.rst.)
This code is not correct in at least two ways:
A. Trying to use metadata keys as email MIME header names is likely to cause all kinds of problems.
If Sweego does not have a native metadata feature, and if sent message headers are available in the webhook payloads, it's acceptable to send metadata using a single JSON-encoded X-Metadata MIME header. See the Scaleway or Resend backends for examples.
B. It silently discards more than five items. (See feedback on set_extra_headers(). This won't be a problem if a single metadata header is used as suggested in A.)
| def set_merge_headers(self, merge_headers): | ||
| # Store merge_headers to apply in serialize_data | ||
| # For /send/bulk/email: variables go in each recipient object | ||
| # For /send (single recipient): variables go in root "variables" field | ||
| if merge_headers: | ||
| self.merge_headers = merge_headers |
There was a problem hiding this comment.
Email headers are not metadata. Does /send/bulk/email support per-recipient email headers?
| # Apply merge_headers and merge_global_data before serializing | ||
| # Use the same logic as get_api_endpoint to determine format | ||
| # Note: Sweego only supports per-recipient variables (merge_headers), | ||
| # not per-recipient headers or metadata | ||
| has_multiple_recipients = len(self.all_recipients) > 1 | ||
| has_per_recipient_data = bool(self.merge_headers) |
There was a problem hiding this comment.
There are two types of sending Anymail requires:
- "Batch send": the
torecipients each receive a separate email showing only their own email address in theTo:header. In a batch send,ccandbccrecipients are copied for eachtorecipient. - Regular send (not batch): a single email is sent showing all recipients in the
To:header.
Use only self.is_batch() to detect batch sends. If the user requested a batch send but the message includes features the ESP does not support for batch sends, use self.unsupported_feature() to report them. Never silently ignore or change the intent of what the user has requested. (E.g., don't convert a cc recipient to a to recipient.)
(Humans: see batch sending docs; AI: please carefully review docs/sending/templates.rst and the various per-recipient merge_* properties and their global counterparts in docs/sending/anymail_additions.rst.)
| if has_multiple_recipients and has_per_recipient_data: | ||
| # Bulk endpoint: variables go in each recipient object | ||
| if self.merge_headers or self.merge_global_data: | ||
| for recipient in self.data.get("recipients", []): | ||
| email = recipient["email"] | ||
| variables = {} | ||
| # Add global variables first | ||
| if self.merge_global_data: | ||
| variables.update(self.merge_global_data) | ||
| # Add per-recipient variables (override global) | ||
| if self.merge_headers and email in self.merge_headers: | ||
| variables.update(self.merge_headers[email]) | ||
| if variables: | ||
| recipient["variables"] = variables | ||
| else: | ||
| # Single recipient (or non-batch): variables go in root "variables" field | ||
| if self.all_recipients: | ||
| email = self.all_recipients[0].addr_spec | ||
| variables = {} | ||
| if self.merge_global_data: | ||
| variables.update(self.merge_global_data) | ||
| if self.merge_headers and email in self.merge_headers: | ||
| variables.update(self.merge_headers[email]) | ||
| if variables: | ||
| self.data["variables"] = variables |
There was a problem hiding this comment.
This is confusing email MIME headers (per-recipient merge_headers), template variable substitutions (merge_global_data and per-recipient merge_data), and metadata (per-recipient merge_metadata).
| def set_extra_headers(self, headers): | ||
| # Sweego limits to 5 custom headers | ||
| self.data.update({k: v for k, v in headers.items()}) |
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User input must never be discarded due to ESP limitations.
- The preferred approach is to provide the data to the ESP and let it return an API error.
- If the ESP's API ignores its own limitations or otherwise mishandles input, instead use
self.unsupported_feature()to report the problem to the user. Only truncate user data ifself.unsupported_feature()returns without raising an error.
| # envelope_recipient: typically the first To address | ||
| if to_list: | ||
| message.envelope_recipient = to_list[0].get("email") | ||
| else: | ||
| message.envelope_recipient = None |
There was a problem hiding this comment.
Don't guess. If Sweego does not provide the SMTP envelope recipient, don't set it.
| # ============================================================================= | ||
| # Inbound Webhook Tests | ||
| # ============================================================================= | ||
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| @tag("sweego") | ||
| class SweegoInboundWebhookTestCase(WebhookTestCase): |
There was a problem hiding this comment.
Please move this to a separate test_sweego_inbound.py file. (See other ESP tests for examples.)
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| # Use pyenv-virtualenv to manage a venv for local development | ||
| .python-version | ||
| deps.json |
There was a problem hiding this comment.
What is this? Use local gitignore mechanisms for developer-specific tools.
| # Extract from address | ||
| from_data = esp_event.get("from_", {}) | ||
| from_email = from_data.get("email", "") | ||
| from_name = from_data.get("name", "") |
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There is a lot of repeated (and non-Pythonic) code in this method for address handling. Please clean it up.
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| return content.decode(encoding, errors="replace") | ||
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| def get_filename(self): |
There was a problem hiding this comment.
This method signature doesn't match the base class's. Is there a reason?
3 participants
Description
This PR adds support for Sweego, a French email service provider specializing in transactional email and SMS.
Relates to #456
Features
Sending
/sendand/send/bulk/emailAPIs (automatic selection){{ variable }}syntaxTracking Webhooks
Inbound Webhooks
Implementation Highlights
Two API Endpoints
Sweego provides two distinct APIs for sending:
/send: For single recipient (variables at root level)/send/bulk/email: For multiple recipients (variables per recipient)Anymail automatically selects the appropriate endpoint based on the number of recipients in the message. Both endpoints support templates and personalization, but with different JSON structures.
Lazy-Loading Attachments (Inbound)
Sweego's inbound webhooks send only attachment metadata (uuid, name, content_type, size). The actual content must be fetched separately via API.
Benefits:
Implementation:
SweegoLazyAttachmentclass that fetches content on-demand when accessed and caches it.Tests
Integration Tests
Integration tests are included in
tests/test_sweego_integration.py.To run them, set the following environment variables:
Then run:
Documentation
Comprehensive documentation in
docs/esps/sweego.rst(604 lines):References
Notes for Reviewers
Lazy attachments: This is the first Anymail implementation of on-demand attachment fetching. Alternative approaches considered but this matches Sweego's API design most naturally.
Dual endpoints: The two APIs (
/sendvs/send/bulk/email) have different JSON structures. Anymail abstracts this complexity - users don't need to know which endpoint is used.MX record: Inbound uses
inbound.sweego.co(verified with Sweego docs).I work at Sweego and wanted to make integration easy for Django developers. I've followed patterns from MailerSend/Mailtrap/Resend implementations. Happy to adjust based on your feedback!