A couple of questions:
-You said the recipient gets an empty message. If you have added a written text message under the image, does recipient get/see the written part of the message?
-Is this happening with one recipient or with all recipients?
-if you take a test pic with the cam built into the MBA(don’t process the image at all) and send it to the recipient using Share>messages, do they successfully see that image?
-if you use your iPhone’s iMessage to text the same image to the recipient, does the recipient now successfully see the image? [after sending the text image from the MBA, that will now be in your iPhone’s iMessage conversation with the recipient].
-What happens if the recipient texts an image to you, do you see the image in iMessage on the MBA?
what I’d look to do (and why I asked the questions above) is isolate this down to who/where the issue lives. This could be your MBA, or the recipient’s device (for some reason maybe it can’t read the pic format you’re sending), possibly filtering by your ISP or telco. I use iMessage on my MBA often to send/receive images.