Halliday, sorry if you felt interrogated or deposed. You said you expect better of me. I’ll give you my best. Since you are a scientist, please try this experiment. Let’s remove Microsoft as a variable; no Outlook, no 365/Exchange.
On an iPhone running iOS 14, open Photos. Select a photo and click the upload icon. Select the native built-in app, Mail. Using either an iCloud.com or gmail.com account (don’t use Hotmail or any other Microsoft account) send the picture to your iCloud or Gmail address. How did it arrive? For me, it came embedded. Now the real moment of truth. Open Sent Items. Open the email you just sent. Is the picture embedded? If so, then I ask you - “What’s Microsoft got to do with that?”
PS - you claim to have mentioned the IETF previously. I went through all 45 pages and didn’t see you mention them specifically; only mentioning the generic “internet protocol standards”. I had to investigate who creates those standards. To your credit, it appears to be legit. It would have been helpful if you included a link to their mission earlier to lend credence to your explanation. However, I have yet to get a reply to my request for them to read this thread and provide their expert opinion. I also asked them to leverage their influence to get resolution; I don’t care if the issue with with Apple (it is) or Microsoft. Surely they write the protocols and standards so they must have some clout in the industry.
Friend of the internet who came here desperate for a solution to send an picture as an attachment to an email, there’s good and bad news. The bad news is that there is not a setting in the built-in Mail app. The good news is that there is a work-around - simply install the Outlook app; it will work with non-Microsoft accounts, such as Gmail or your favorite ISP. Maybe one day Apple will fix it (or Microsoft if you’re buying what my scientist friend is selling). If it’s never fixed, then get used to the Outlook app. You can actually have both the Outlook app and built-in Mail app configured for the same account. You only have to use the Outlook account whenever you want to send a picture as an attachment.
Congrats to those of you who scrolled through 45 pages of commentary without a suggestion for a work-around. My apologies for the amount of time you wasted. Peace ☮️ ✌🏻