I have to disagree with your thesis that MailDrop is a phantom that does not work. I had not consciously tried to force MailDrop before you bought this up, but after my experiments I am convinced that it does work but as logic would dictate, when emailing large files the actual point to point delivery time may be longer than a standard email with small attachments. That said, I have now activated MailDrop for all of my IMAP accounts and I will most definitely be intentionally relying on it for large file movements in the future. I have not read David Pogue's Yosemite: The Missing Manual but from your description I would whole heartedly concur with his enthusiasm for the tool.
Now that I know I can receive large email attachments on my iOS as well as MacOS devices and thanks to MailDrop I can send those large email attachments using MacOS, I have to find out if I can send large attachments using iOS devices. I can envision a number of uses for it.:
