I’m not certain this is a new problem or one that has been around that I’m just now seeing. I was forwarded an email that contains embedded photos. In K9, I cannot see the photos, only the text with reference numbers for the photos, such as [cid:bc0d5854-1c22-456c-b084-…] etc. At the bottom of the email, I can see small broken graphic icons saying, “image.png”.
When I look at the same email on my desktop using Outlook, the photos are properly embedded within the original email body. I believe the person that composed the original email as well as the person that forwarded the email to me were both using Outlook.
I believe this has something to do with the fact that the message was forwarded, as I’m able to see the auto-signature icon from the person that sent the message to me, but not from the person that sent it to him (when viewed on my phone).
I’m running K9 v8.2 with Android 14. I do have Settings>Accounts>Reading Email set to “Always show images from anyone”.
You must’ve misunderstood my write-up. The email was forwarded to me; I did not forward it.
However, this gave me an idea. I forwarded that email using K9 to another email account and used Thunderbird (desktop) on a PC to read it; the embedded pictures came through and displayed just fine.
I just tried another experiment. I contacted the person that forwarded the email to me and had him forward it again using his phone (just to prove repeatability) AND forward it again from his desktop PC, which uses Outlook. Once again, for the email forwarded from his phone, I could not see the embedded pictures in K9, but I could see the embedded pictures for the email sent from Outlook. For both test emails, I could see the pictures just fine in Outlook on a PC.
I knew he was using an iPhone, but I didn’t know what email client he was using. He said he was using the built-in mail application.
So, my conclusion, based on this testing, is somehow the iPhone mail app is encoding the forwarded email (that contains the embedded pictures) in a way that K9 is unable to properly display, but desktop email applications, such as Outlook and Thunderbird, can display it just fine.
In general, embedded images require HTML as they are stored as base64 data blobs in the message source code. K-9 does not support HTML as other email programmes or apps do.
As some programmes/apps do not support HTML and/or users disable HTML for security reasons, many programmes/apps dual-encode emails. The message itself is put first into the mail body (i.e., the data blob after the first CRCLCRLF) as plain text, and then put the same message as formatted HTML or RTF into MIME multipart body.
Thus, K-9 won’t show the images as it displays the plain text message from the body, while other programmes/apps will show the images as they display the formatted MIME attachment.
Thank you for the explanation. I figured it had to be something the way the message was encoded/formatted. Though this incompatibility has probably existed for years, this was the first time it really caught my attention because I couldn’t see what it was he was asking me to look at until I could get to my desktop PC.