An error occurred while saving the commentChris commented
Bump. The issue seems to apply to local images (i.e., if you take it off your hard drive and drop it into the email body, it will show to you, even in your sent box once you've sent the email, but it will not show on the recipients end). I've tested this for multiple recipients in gmail and it simply does not show. The only way to display the image directly is to link to it directly via an image fileshare website in the source code, i.e., Imgur, Tinypic, ImageShack, etc.
2. To this end, it's still quite hard since image sharing websites are not listed as services you can link to in Airmail 3; only services like dropbox etc, which do not enable you to copy an image's path directly, and hence there's no easy way of displaying images in emails. Please add imgur, tinypic, etc. which alllow you to copy a direct link to the image, into the source code of the email. This will enable an interim workaround for html savy customers to display pics to their associates. As for other customers or customers who simply pay for convenience, please support local image drop into emails displaying to recipients like they do in most email UIs; e.g, Gmail.