Hi there,

> I might be wrong, but I don't think the Gnus agent can be easily reused
> from notmuch. We could perhaps save the message as a draft upon C-c C-j,
> and then have a periodic timer that checks if any of the drafts has
> expired (maybe using a special, additional tag for the search) and send
> it?

I have solved this myself using `gnus-delay-article` as a basis.

I am attaching here my current code, it is my intention to (time
permitting) turn this over a patch for inclusion into notmuch itself.

What is preventing such patch right now:

- Writting tests,
- I'm trying to find something like `killing-new-buffers` builtin but
  will probably just include the code.

A side of the attached file you will need the `killing-new-buffers`
macro, pasted below.

(defmacro killing-new-buffers (&rest body)
  "Run BODY and kill any buffers that were not already open."
  (declare (debug t))
  (cl-with-gensyms (initial-buffers) 
    `(let ((,initial-buffers (buffer-list)))
       (unwind-protect
	   ,(macroexp-progn body)
	 (dolist (b (buffer-list)) (unless (memq b ,initial-buffers) (kill-buffer b)))))))

Hope this helps,

marc