>> In contrast, Thunderbird and Alpine show that there is an attachment (that one can save, open, etc.).
It's just a way to deal with malformed messages -- sent by malformed mail apps -- which mark images as "inline" and don't actually reference them from HTML content.
Yep, I understand, and while it is not required, it is a good behavior.
Besides compensating for a malformed message, it allows people to save one of the "parts/attachments" separately, even in the graphic-capable program such as Thunderbird.
As for Alpine (aka a followup to pine), - since it is a terminal (text)-based program itself, - it shows ALL parts of the multipart message as "Parts/Attachments", without making a distinction:
Parts/Attachments:
1.1 OK ~436 bytes Text (charset: UTF-8)
1.2 Shown ~682 bytes Text (charset: UTF-8)
2 3.6 MB Image
But I think there is another case here.
Sending a message like that (original with inlines, turning off quoting when replying) -- *and then* opening it from Sent and doing "Edit as new".
Am I right? Is the new scenario you've just discovered?
Nope.
I had two other scenarios that I encountered (one in part of the course of interaction, the other one, - in the course of testing):
1. I replied with the malformed message (from the older version of AM), then I got response to my message that preserved that phantom inline image. While trying to reply to that message with the new, "fixed" version, I was still having that phantom inline image.
I don't know what client was used on the other end to preserve that phantom image, but I wasn't happy to keep both receiving and sending it (bloating my mailbox and wasting my cell data allowance)
2. I sent a copy of a reply to myself, and so, I was testing by replying to myself from the newer version of AM.
I don't want to waste your (and) time anymore on this. It is sort of a "marginal" case, and most likely it is not affecting many people. (and even when it is happening, most people probably wouldn't notice.)
So, if it requires somewhat considerable effort, don't bother.
If it is easy, it would be nice to have an option to see the presence of any of phantom part.
While writing this message I thought of one more case where this behavior may play a role. And in that case, it should not be limited to an image, but should be extended to any object used or unused.
Consider a message sent with a malware object sent as an inline phantom (i.e. unreferenced) part.
If the recipient using Aquamail responds to that message (to the address faked in the field "From:") or better yet, - forwards it to somebody else (as it is frequently happens with socially engineered "viral" messages), than this user is spreading that malware (which might not be affecting Android but would affect other OSes).
I understand that this is a security consideration that might be beyond the scope of your interests. Also, even this case is probably rare enough... So, as I wrote above, I stop at this.
