On Feb 23, 2010, at 8:14 PM, Glenn Morris wrote:
> + ;;;###autoload(custom-initialize-delay 'send-mail-function nil)
> + 
>  ;;;###autoload
>  (defcustom mail-header-separator (purecopy "--text follows this line--")

That's a smaller change and maybe the right thing to do right now, but I'd still like to understand why you accept the initialization mechanism in startup.el to init only at dump time and not at run-time in the case of send-mail-function. That's what seemed to be the real problem.  Adding code to loaddefs.el seems like a workaround.

Btw. I considered a solution like yours, but I didn't figure you could do this sort of thing with the ###autoload cookies.  I thought, from a comment in autoload.el, that they were restricted to defcustoms and defuns.