[MlMt] Inline images have "attachment" disposition and this may cause problems with ProtonMail

[Oli Sturm]

Quick follow-up: I tried using Thunderbird with ProtonMail Bridge, and the same inline image test case works fine. Thunderbird uses Disposition: inline, and the Content-ID is retained as you would expect.

Can we have MailMate do the same?

On 24 Feb 2025, at 12:06, Oli Sturm via mailmate wrote:

> Hi,
>
> I’m using ProtonMail Bridge and I see some odd behavior with MailMate. One strange thing is that during its detailed reformatting of messages, ProtonMail (PM) seems to drop the Content-ID properties of inline images, which breaks the img src attributes in the HTML parts, so that these images are not displayed on the recipient’s side.
>
> When I cross-checked what PM itself generates when I send a similar email, I found that they use Content-Disposition: inline for inline images… which makes good sense to me. I wonder whether the Content-IDs are dropped by their system in cases where the disposition is attachment, but preserved for disposition inline.
>
> And I wonder why MailMate doesn’t use inline where it seems to make very good sense to do so. I’m no RFC guru in these areas, so I may well be completely wrong here… but is there any chance there could be an MM bug here, or at least a situation where an option may be provided in case it helps compatibility?
>
> Thanks
> Oli
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