[pcbeingused333]

Forwarding an inbound email with passthrough breaks inline images.

Cause. In ReceivingSvc::forward with passthrough, the attachment Content-ID was read with MailHeader::get_key(), which returns the header name. Every inline attachment was therefore re-sent with content_id = "Content-ID", and cid: references in the HTML no longer resolved.

Fix. Read the header value with get_value() and strip the surrounding </>. The attachment mapping moved into a small passthrough_attachments(&[u8]) helper so it can be unit tested without the network (behaviour otherwise unchanged). Added a CHANGELOG entry.

Test. receiving::test::passthrough_keeps_attachment_content_id builds a multipart message with Content-ID: <logo@example.test> and asserts the serialized attachment has content_id == "logo@example.test" (red before: "Content-ID").

Reproduction

Raw message: a multipart/mixed part with Content-Disposition: attachment; filename=logo.png and Content-ID: <logo@example.test>; cargo test --lib passthrough.

---

This PR was prepared with the assistance of an AI tool (Claude Code).

---

Summary by cubic

Fixes forwarding inbound emails with passthrough so inline images keep working.

The passthrough path read the Content-ID header name instead of its value, so attachments were re-sent with content_id = "Content-ID" and cid: references in the HTML no longer resolved.

• Reads the header value and strips the surrounding angle brackets.
• Collects attachments across the whole MIME tree, so nested parts and inline cid: images are kept.
• Re-sends the original text/HTML body when the caller doesn't supply one.
• Falls back to the Content-Type name parameter for filenames and allows attachments without a filename.
• Moved extraction into passthrough_content helpers with unit tests; bumped to 0.35.3 and updated the CHANGELOG.

^{Written for commit 8cbc065. Summary will update on new commits.}

[AntoniosBarotsis]

Thanks! Found a few more edge cases compared to the node implementation so updated those as well, releasing 0.35.3 in a few minutes!