Support CID embeds

[ToshY]

Problem

For Symfony projects I've switched from Mailtrap to Mailcrab, and I've just noticed that images embedded with CID are not being displayed in Mailcrab's formatted view.

Raw (truncated email example)

MIME-Version: 1.0
Date: Sat, 27 May 2023 14:45:54 +0200
Content-Type: multipart/related; boundary=VALLHhYX

--VALLHhYX
Content-Type: multipart/alternative; boundary=1mS-w7PU

--1mS-w7PU
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable

--1mS-w7PU
Content-Type: text/html; charset=utf-8
Content-Transfer-Encoding: quoted-printable

<img src=3D"cid:03487338a9ba70e29f37dd06781f9a95@symfony" alt=3D"">
--1mS-w7PU--

--VALLHhYX
Content-ID: <03487338a9ba70e29f37dd06781f9a95@symfony>
Content-Type: image/png; name="03487338a9ba70e29f37dd06781f9a95@symfony"
Content-Transfer-Encoding: base64
Content-Disposition: inline;
 name="03487338a9ba70e29f37dd06781f9a95@symfony";
 filename="@images/favicon.png"

<base64-string-here>
--VALLHhYX--

As you can see in the raw example above, the image src with cid 03487338a9ba70e29f37dd06781f9a95@symfony is available, which contains a base64 encoded string of the image file. But the image itself is available in the email as an attachment instead of being embedded.

So it just shows the broken image icon in the formatted view.

Proposal

Support for CID embeds.

[stappersg]

On Sat, May 27, 2023 at 06:14:12AM -0700, ToshY wrote: ... I've just noticed that images embedded with CID are not being displayed in Mailcrab's formatted view.

...

**Proposal**

I spell feature request differently :-)

Support for CID embeds.

Advice for Toshy: Make reproducing the inconvenience possible

[ToshY]

@stappersg I'm somewhat confused on what more you would want to see exactly. The raw example response is what I got from the Raw tab in Mailcrab and I removed unncessary html bloat (while keeping content type headers) to show that both the image tag <img src=3D"cid:03487338a9ba70e29f37dd06781f9a95@symfony" alt=3D""> and Content-ID: <03487338a9ba70e29f37dd06781f9a95@symfony> are in there, but Mailcrab evaluates this as an attachment instead of displaying the embedded image in the Formatted view.

I'm not sure if the issue statement is unclear or the definiton of CID embeds? Here's an SO post explaining how they work, showing a similiar response as the example I've provided.

If you insist on having a reproduction case, I can make one in Symfony 6.x (PHP 8.1) even though that has nothing to do with the issue, as the same email gets handled correctly by other mail clients (Mailtrap/Gmail/etc.).

---

As this library is inspired by Mailhog, you can find the same issue there as well: mailhog/MailHog#27

[marlonbaeten]

Thanks for reporting this @ToshY. This should be fixed - I'll try to implement it soon.

[marlonbaeten]

This is fixed in v0.19.0 👍