Sorry, what I wrote last night was (1) not clear and (2) wrong. What I meant to write was that to include images in HTML messages sent by SENDHTML, I would put or find the image on a web server and reference it in the message using its URL as
<img src="http...">
What I often wanted to do was to encode the image in the message itself and reference it as a file, using
<img src="filename">
That's what I thought that the /image option for the SENDHTML command would implement. Way back earlier in the year, I think I figure out some details of this issue, but I don't remember them now.